ANSYS System Coupling Users Guide

System Coupling User's Guide

Release 16.0ANSYS, Inc.January 2015Southpointe

2600 ANSYS DriveCanonsburg, PA 15317 ANSYS, Inc. is

certified to ISO9001:2008.

[email protected]://www.ansys.com(T) 724-746-3304(F) 724-514-9494

Copyright and Trademark Information

© 2014-2015 SAS IP, Inc. All rights reserved. Unauthorized use, distribution or duplication is prohibited.

ANSYS, ANSYS Workbench, Ansoft, AUTODYN, EKM, Engineering Knowledge Manager, CFX, FLUENT, HFSS, AIMand any and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarksor trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademarkused by ANSYS, Inc. under license. CFX is a trademark of Sony Corporation in Japan. All other brand, product,service and feature names or trademarks are the property of their respective owners.

Disclaimer Notice

THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFID-ENTIAL AND PROPRIETARY PRODUCTS OF ANSYS, INC., ITS SUBSIDIARIES, OR LICENSORS. The software productsand documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreementthat contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exportinglaws, warranties, disclaimers, limitations of liability, and remedies, and other provisions. The software productsand documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditionsof that software license agreement.

ANSYS, Inc. is certified to ISO 9001:2008.

U.S. Government Rights

For U.S. Government users, except as specifically granted by the ANSYS, Inc. software license agreement, the use,duplication, or disclosure by the United States Government is subject to restrictions stated in the ANSYS, Inc.software license agreement and FAR 12.212 (for non-DOD licenses).

Third-Party Software

See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary softwareand third-party software. If you are unable to access the Legal Notice, please contact ANSYS, Inc.

Published in the U.S.A.

Table of Contents

About This Manual ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiDocument Conventions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiTechnical Support ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

System Coupling Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Supported System Couplings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Product Licensing Considerations when using System Coupling .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

System Coupling Workspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Setting Up a Simulation that Uses System Coupling .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Components of the System Coupling Workspace .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Outline View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Properties View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8System Coupling Chart View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Solution Information View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Settings for Completing a System Coupling Setup .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Analysis Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Analysis Type .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Initialization Controls ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Coupling Initialization .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Duration Controls ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Duration Defined By .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Step Controls ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Analysis Settings Best Practices .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

General Analysis Type .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Transient Analysis Type .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Participants .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Working with Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Data Transfer Rules .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Execution Control ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Co-Simulation Participant Sequencing .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Sequential Solutions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Simultaneous Solutions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Debug Output Control ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Intermediate Restart Data Output .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Validation and State of the System Coupling Setup Cell .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23System Coupling Setup Cell Context Menus .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Expert Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Settings for Running a System Coupling Solution .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Solution Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28System Coupling Chart ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Chart Properties ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Chart Variable .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Chart Variable Properties ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Working with System Coupling Charts ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Using the System Coupling Chart View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Validation and State of the System Coupling Solution Cell .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32System Coupling Solution Cell Context Menus .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Workflows for System Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Executing System Couplings Using the Command Line .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

System Coupling Command Line Options .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

iiiRelease 16.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

Restarting a System Coupling Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Generating Restart Files ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Executing the Restart Run .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Recovering from a Workbench Crash .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Stopping the Coupled Analysis Run .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Understanding the System Coupling Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Coupling Management .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Inter-Process Communication .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Process Synchronization and Analysis Evolution .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Convergence Management .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Evaluating Convergence of Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Data Pre-Processing Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Creating Nodal Data from Face/Element Centroid Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Creating Face/Element Data from Node Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Mapping Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Data Transfer Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Profile Preserving .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Conservative Profile Preserving .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Bucket Surface .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48General Grid Interface (GGI) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Interpolation Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Interpolated Data Post-Processing Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Ramping Algorithm ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Under-Relaxation Algorithm ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Initial Values used in Ramping and Under-Relaxation Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Clipping Algorithm ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Files Used by the Coupling Service .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55System Coupling Service Input File (scInput.sci) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55System Coupling Service Shutdown File (scStop.stop) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Files Generated by Coupling Service .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56System Coupling Server File (scServer.scs) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56System Coupling Service Log File (scLog.scl_, scLog_##.scl) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57System Coupling Results File (scResults_##_######.scr) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Understanding the System Coupling Input File ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Understanding the System Coupling Log File ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Best Practice Guidelines for Using System Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Building up a Coupled Analysis from Decoupled Systems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Troubleshooting Two-Way Coupled Analyses Problems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Using Text-Based Monitor Output to Debug Coupled Analyses .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74Using Graphical Monitor Output to Debug Coupled Analyses .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Using Supplemental Output to Debug Coupled Analyses .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Supplemental Output for Diagnosing Mapping Problems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Improving Coupled Analysis Stability ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Data Transfer Ramping .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Participant Solution Stabilization .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Co-Simulation Participants Sequencing ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Controlling Participant Sequencing .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Using Sequencing to Reduce Coupled Solution Execution Time .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Tutorial: Oscillating Plate with Two-Way Fluid-Structure Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Overview of the Problem to Solve .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Creating the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Release 16.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationof ANSYS, Inc. and its subsidiaries and affiliates.iv


Optional: Preparing for a Command-line Run .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Adding Analysis Systems to the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Adding a New Material for the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Adding Geometry to the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Defining the Physics in the Mechanical Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Generating the Mesh for the Structural System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Assigning the Material to the Geometry .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Setting the Basic Analysis Values .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Inserting Loads .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Defining the Fixed Support ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Defining the Fluid-Solid Interface .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Defining the Pressure Load .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Preparing for a Command-Line Run of the Structural System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Completing the Setup for the Structural System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Setting up your Fluid Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Generating the Mesh for the Fluid System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Defining the Physics in the ANSYS Fluent Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Adding the Solution Setup Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Defining the Dynamic Mesh .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Adding the Solution Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Preparing for a Command-Line Run of the Fluent System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Defining and Running the Coupling in the System Coupling Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97Setting the Basic Analysis Values .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98Creating the Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98Preparing System Coupling for Restarts ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Solving and Restarting the Coupled Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Preparing for a Command-Line Run of the System Coupling System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Viewing Results in CFD-Post ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Creating an Animation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Plotting Results on the Solid .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Post-Processing in Mechanical ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Setting Up and Executing a Coupled Analysis Restart from Workbench .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104Executing the Coupled Analysis from the Command Line .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Preparing the Required Input Files ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106Running the Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106Restart Analysis Execution .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Preparing the Required Input Files ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108Run the Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108Loading the Results into CFD-Post ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Tutorial: Heat Transfer from a Heating Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Overview of the Problem to Solve .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Part 1: Transferring Data from the Steady-State Thermal Analysis to the Fluid Flow Analysis ... . . . . . . . . . . . . . . . 112

Creating the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112Setting the Units in ANSYS Workbench .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Adding Analysis and Component Systems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113Adding New Materials for the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Adding Geometry to the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Preparing the Steady-State Thermal Source Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Assigning the Material to the Geometry .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Generating the Mesh .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Defining the Physics for the Structural Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Defining the Steady-State Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

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Executing the Structural Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117Post-Processing the Structural Analysis Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Using External Data to Access the Steady-State Thermal Source Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119Preparing the Fluid Flow Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Importing the Mesh for the Fluid Flow Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Defining the Physics for the Fluid Flow Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Preparing and Executing the Coupled Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Reviewing Results in CFD-Post ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Part 2: Transferring Data from the Fluid Flow Analysis to the Steady-State Thermal Analysis ... . . . . . . . . . . . . . . . 126Exporting the Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126Adding Additional Analysis and Component Systems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127Using External Data to Access the Fluid Flow Source Data ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Preparing the Steady-State Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Preparing and Executing the Coupled Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Reviewing Results in the Mechanical Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Index .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

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About This ManualThis manual describes how to use the System Coupling component to control otherwise independentphysics solvers or external data sources so that they work together in a coupled analysis such as Fluid-Structure Interaction (FSI).

This manual contains the following chapters:

• System Coupling Overview (p. 1) describes how System Coupling works and the types of simulations youcan perform.

• System Coupling Workspace (p. 7) describes how to use the System Coupling views in ANSYS Workbenchto control the analysis.

• Workflows for System Coupling (p. 33) describes common workflow topics such as using the command line,and restarting coupled analyses

• Understanding the System Coupling Service (p. 41) describes files used by the Coupling Service, the com-munication technology, the run time environment, and the mapping technologies.

• Best Practice Guidelines for Using System Coupling (p. 73) describes best practices for using System Coupling.

• Tutorial: Oscillating Plate with Two-Way Fluid-Structure Interaction (p. 79) guides you through performingan example of a coupled analysis.

• Tutorial: Heat Transfer from a Heating Coil (p. 111) demonstrates how to execute a sequence of one-waythermal transfers in a heat exchanger using System Coupling.

Document Conventions

This section describes the conventions used in this document to distinguish between text, file names,system messages, and input that you need to type.

File and Directory NamesFile names and directory names appear in this font:/usr/lib.

User InputInput you must type exactly is shown like this:

cd /usr

Input SubstitutionInput that you must supply in a command is shown like this:

fluent 3d -schost="HostName"

That is, you should actually type fluent 3d -schost=" " and substitute a computer's namefor HostName.

Optional ArgumentsOptional arguments are shown using square brackets:

export -cgns [-verbose] file

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Here the argument -verbose is optional, but you must specify a suitable file name.

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If your support is provided by ANSYS, Inc. directly, Technical Support can be accessed quickly and effi-ciently from the ANSYS Customer Portal, which is available from the ANSYS Website (www.ansys.com)under Support > Customer Portal. The direct URL is: support.ansys.com.

One of the many useful features of the Customer Portal is the Knowledge Resources Search, which canbe found on the Home page of the Customer Portal. To use this feature, enter relevant text (errormessage, etc.) in the Knowledge Resources Search box and click the magnifying glass icon. TheseKnowledge Resources provide solutions and guidance on how to resolve installation and licensing issuesquickly.

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About This Manual

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About This Manual




System Coupling Overview

The ANSYS suite of analysis software facilitates creation of a spectrum of single- and multidisciplinarysimulations. Multidisciplinary simulations are offered within the context of a single piece of software(for example, within one solver) and using various dedicated mechanisms to couple a single piece ofsoftware with others. Examples of the latter include mechanisms to import external data from staticsources, and the Multi-Field External (MFX) solver used for co-simulation between ANSYS MechanicalMAPDL and ANSYS CFX. These coupling mechanisms provide optimal solutions for the analyses thatfollow the single, specific workflow that they were built to solve.

The System Coupling infrastructure discussed in this manual should be considered for generic workflowsinvolving any number of analysis types, static data source and co-simulation participants, and datatransfer quantities and directions. The Workbench System Coupling component system is an easy-to-use, all-purpose infrastructure that facilitates comprehensive multidisciplinary simulations betweencoupling participants.

Coupling participants are systems that will provide and/or consume data in a coupled analysis. Examplesystems in Workbench include:

• Analysis Systems – Steady-State Thermal, Transient Thermal, Static Structural, Transient Structural, FluidFlow (Fluent)

• Component Systems – Fluent, External Data

The execution of analyses involving couplings between any of these participants is managed by theSystem Coupling Service, which is the runtime component of the System Coupling system. During exe-cution, a variety of one- and two-way data transfers are performed between coupling participants. Forexample, when multiple participants are executing their parts of a coupled analysis together, which isoften referred to as co-simulation, they may engage in both one- and two-way data transfers as eithera source or target. Similarly, when participants are providing access to existing results or data, whichshall be referred to as a static data source, they may engage in only one-way data transfers as a source.

This documentation provides a detailed description of capabilities supported by the System Couplingcomponent system. All of these capabilities may, however, not yet be supported in conjunction withother Workbench systems. For information about systems that may act as participants in system couplings,see the summary of Supported System Couplings (p. 3).

For information regarding product licensing details and interactions with System Couplings, see ProductLicensing Considerations when using System Coupling (p. 4).

To set up and execute a system coupling simulation, perform the following steps:

1. Create the project.

2. Add the individual, participant systems to the project.

3. Add the System Coupling system to the project.

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4. Set up each individual, participating system (generally from top-to-bottom, until you have completed allthe required steps for your analysis).

5. Connect the systems together as shown in Figure 1: Example of Connecting a System Coupling ComponentSystem with Various Types of Systems (p. 2). For co-simulation participants and the External Data staticdata participant, connections are drawn from the participants’ Setup cells.

6. Set up the System Coupling system (see System Coupling Workspace (p. 7)).

Figure 1: Example of Connecting a System Coupling Component System with Various Types ofSystems

It is important to note that updates of co-simulation participant (for example, a solver) Solution cellsare disabled for Workbench systems connected to the System Coupling system; these updates (andexecution of the respective solvers) are automatically initiated when the System Coupling Solution cell

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is updated. Note, however, that these updates respect all settings (for example parallel, precision, andso on) already made for them.

Important

Using System Coupling in conjunction with the Remote Solver Manager (RSM) is not supported.In the isolated case of Mechanical, the use of RSM for runs on a single local host is, however,permitted.

After you have updated the System Coupling Solution cell, you can:

• Pause the analysis by interrupting its progress.

• Restart the analysis as described in the Initialization Controls (p. 10).

• Debug your system coupling simulation by using the system coupling command line arguments (see SystemCoupling Command Line Options (p. 34)). You can also perform additional debugging of the connectedsystems as described in Troubleshooting Two-Way Coupled Analyses Problems (p. 73).

• Use CFD-Post to simultaneously analyze the results of the simulation by:

– Connecting other participant systems’ Solution cells to the Results cell of the Fluid Flow system, or

– Connecting all participant systems’ Solution cells to a Results component system that you introduce inthe schematic.

Supported System Couplings

The following is the list of supported coupling participants:

• Fluent

• Static Structural

• Transient Structural

• Steady-State Thermal

• Transient Thermal

• External Data

Fluent can be connected with any of the other supported participants. In addition, the Steady-StateThermal system can be connected with external data. Note that Steady-State and Static systems cannotbe coupled with Transient systems.

Note

Only two coupling participants can be connected to the System Coupling system at onetime. However, more than one System Coupling system may be introduced within the sameproject schematic.



Supported System Couplings

For information about using System Coupling with the ANSYS Fluent system in Workbench, see Perform-ing System Coupling Simulations Using Fluent in Workbench in the Fluent in Workbench User's Guide.For information about restarting a coupled analysis with Fluent, see Restarting Fluent Analyses as Partof System Couplings.

For information about using System Coupling with the ANSYS Mechanical system in Workbench, seeSystem Coupling in the ANSYS Mechanical User's Guide. For information about restarting a coupledanalysis with Mechanical, see Restarting Structural Mechanical Analyses as Part of System Coupling.

For information about using System Coupling with the External Data system in Workbench, see ExternalData.

Product Licensing Considerations when using System Coupling

The licenses needed for System Coupling analyses are listed in Table 1: Licenses Required for ParticipatingSystems in System Coupling (p. 4). No additional licenses are required for the System Coupling infra-structure.

The simultaneous execution of coupling participants currently precludes the use of the license sharingfeature that exists for some product licenses. The following specific requirements consequently exist:

• Distinct licenses are required for each coupling participant.

• Licensing preferences should be set to ‘Use a separate license for each application’ rather than ‘Sharea single license between applications when possible.’

The requirements listed above are particularly relevant for ANSYS Academic products.

Table 1: Licenses Required for Participating Systems in System Coupling

Academic License RequiredCommercial LicenseRequired

System

Fluent • ANSYS Academic Associate,• ANSYS CFD,

• ANSYS Fluent, or • ANSYS Academic Associate CFD,

• ANSYS Academic Research,• ANSYS Fluent Solver

• ANSYS Academic Research CFD,

• ANSYS Academic TeachingAdvanced,

• ANSYS Academic TeachingIntroductory, or

• ANSYS Academic Teaching CFD

StaticStructural or

• ANSYS Academic Associate,• ANSYS Structural,

• •ANSYS Mechanical, ANSYS Academic Research,TransientStructural

•• ANSYS Academic ResearchMechanical,

ANSYS Mechanical CFD-Flo,

• ANSYS Mechanical Emag,



Academic License RequiredCommercial LicenseRequired

System

• ANSYS Academic TeachingAdvanced,

• ANSYS Multiphysics,

• ANSYS Structural Solver,• ANSYS Academic Teaching

Introductory, or• ANSYS Mechanical Solver,or

• ANSYS Academic TeachingMechanical• ANSYS Multiphysics Solver

Steady-StateThermal or

• ANSYS Academic Associate,• ANSYS Mechanical,

• •ANSYS Mechanical CFD-Flo, ANSYS Academic Research,TransientThermal

•• ANSYS Academic ResearchMechanical,

ANSYS Mechanical Emag,

• ANSYS Multiphysics,• ANSYS Academic Teaching

Advanced,• ANSYS Structural Solver,

• ANSYS Mechanical Solver,or

• ANSYS Academic TeachingIntroductory, or

• ANSYS Multiphysics Solver • ANSYS Academic TeachingMechanical

No license is needed to run External Data.ExternalData



Product Licensing Considerations when using System Coupling


System Coupling Workspace

This chapter discusses the following topics:Setting Up a Simulation that Uses System CouplingComponents of the System Coupling WorkspaceSettings for Completing a System Coupling SetupSettings for Running a System Coupling Solution

Setting Up a Simulation that Uses System Coupling

The general workflow for setting up a System Coupling simulation is presented in System CouplingOverview (p. 1).

Most participant systems with connections originating from their Setup cells will participate in theanalysis in a co-simulation mode (visually indicated in the Project Schematic with connections betweenthe Setup cells, and different icons and colors for the Solution cells). The exception to this is the ExternalData participant system, since a connection originates from its Setup cell, but it acts as a static dataparticipant. The Update option is disabled from within the right-click menu of the co-simulation parti-cipant systems' Solution cells because the update (and solution execution) is now controlled by theSystem Coupling Solution cell.

Note that using System Coupling in conjunction with the Remote Solver Manager (RSM) is not supportedfor runs on multiple host machines. In the isolated case of Mechanical, the use of RSM for runs on asingle local host is, however, permitted.

The System Coupling system in the Project Schematic has two cells:

• Setup: Use this cell to see participant, region, and variable information, and to define analysis settings anddata transfer between participants. Double-click the Setup cell, or right-click and choose Edit from thecontext menu to display the System Coupling workspace.

• Solution: Use this cell to solve a coupled analysis and to see solution information and charts monitors.Double-click the Solution cell, or right-click and choose Edit from the context menu to display the SystemCoupling workspace.

Components of the System Coupling Workspace

When you edit the Setup or Solution cells of the System Coupling component system, the same SystemCoupling workspace is displayed in a tab within your workbench project. The Outline view, Propertiesview, System Coupling Chart view, and Solution Information view are displayed by default. For moreinformation about the tabbed views in Workbench, see Workbench Tabs and Views in the WorkbenchUser's Guide.



Figure 2: The System Coupling Workspace

See the following sections for additional information:Outline ViewProperties ViewSystem Coupling Chart ViewSolution Information View

Outline View

The Outline view (in the upper left corner of Figure 2: The System Coupling Workspace (p. 8)) presentsvarious fields related to the coupling participants and to the setup and solution of the coupled systems.The deepest fields can be edited in the Properties view. For additional information, see Settings forCompleting a System Coupling Setup (p. 9) and Settings for Running a System Coupling Solution (p. 28).

Properties View

The Properties view (in the lower left corner of Figure 2: The System Coupling Workspace (p. 8))presents the properties of an editable item selected in the Outline view. For additional information,



see Settings for Completing a System Coupling Setup (p. 9) and Settings for Running a SystemCoupling Solution (p. 28).

System Coupling Chart View

The System Coupling Chart view (in the upper right corner of Figure 2: The System Coupling Work-space (p. 8)) presents chart monitors in the System Coupling workspace during the solution process.For additional information, see System Coupling Chart (p. 29) and Using the System Coupling ChartView (p. 31).

Solution Information View

The Solution Information view (in the lower right corner of Figure 2: The System Coupling Work-space (p. 8)) presents a text-based solution log of information output during the execution of thecoupled analysis. For additional information, see Solution Information (p. 28).

Settings for Completing a System Coupling Setup

This section describes:

• All the settings that appear in the Outline and Properties views under the “Setup” branch.

• Context menus (that is, the menus that appear with a right-click) for the Setup cell.

See the following sections for additional information:Analysis SettingsParticipantsData TransfersData Transfer RulesExecution ControlValidation and State of the System Coupling Setup CellSystem Coupling Setup Cell Context MenusExpert Settings

Analysis Settings

The Analysis Settings field has the following properties:

• Analysis Type

• Initialization Controls

• Duration Controls

• Step Controls

Suggested best practices for analysis settings are discussed in Analysis Settings Best Practices (p. 12).

Analysis Type

This option is used to define the overall coupling type for the analysis.

The available options are:




• General

– This is the only available option when one or more of the coupling participants is executing steady orstatic analyses. Note that mixed steady/static and transient analyses are not currently possible.

• Transient

– This is the only available option when all of the coupling participants are executing transient analyses.

Initialization Controls

This option is used to define the initialization controls available for all coupling types.

Coupling Initialization


• Program Controlled

– For initial runs (that is, not restart runs), the initial time and step are each set to 0.

– For restart runs, the initial time and step are set to the values obtained from the latest valid restart point.

• Restart Points (indicated by Step and Time)

– The system coupling simulation can have multiple restart points when Intermediate Restart Data Out-put (p. 22) is selected for either all coupling steps or for a set of coupling step intervals. The next coupledanalysis will be started based on the restart point that you have selected.

For more information regarding restarts, see Restarting a System Coupling Analysis (p. 35).

Important

Program controlled or explicitly specified restart points only affect the coupling stepand/or time used to restart the coupling service. Appropriate restart points must alsobe specified for the co-simulation participants that are part of the coupled analysis. Formore information about coupling participants, see Restarting a System Coupling Analysis.

Duration Controls

This option is used to define the duration for the analysis.

Duration Defined By

The options available to define the duration of a coupled analysis are:

• End Time

– Available only when the Analysis Type is Transient

– When the End Time option is used, the coupling service will execute coupling steps until the specifiedend time is reached. In a transient analysis, each coupling step is a time step (with the time interval specifiedby the step size). Note that the final coupling step size is reduced automatically, if needed, so that thespecified end time is respected.



– Some of the participant systems, such as ANSYS Mechanical, require the end time specified in their setupto be respected. When a coupled analysis involves one or more participants that require their setup’s endtime be respected, then the maximum allowable end time for the coupled analysis is the minimum of theend times reported by such participants. In this case, a validation error will be reported if the coupledanalysis’ specified end time is greater than the minimum identified.

Other participant systems, such as Fluent, can run past the end time specified. These participantsystems have no effect on the allowable end time of the coupled analysis.

• Number of Steps

– Available only when the Analysis Type is General.

– When this option is used, the coupling service will execute coupling steps until the specified number ofsteps is reached.

Step Controls

The duration of the coupled analysis is broken into a sequence of coupling steps. Data transfers betweenthe coupled solvers occur at the beginning of each coupling iteration within a coupling step. Couplingsteps are always indexed. During the analysis, each new coupling step is started when:

• The coupling analysis duration has not been reached, and

• Either the maximum number of coupling iterations has been reached or the coupling step is converged.


• Step Size

– If the coupling is defined in terms of time (a transient analysis), then a coupling step is associated with atime interval. The Step Size option specifies the time interval associated with each coupling step (inseconds). The final coupling step size is reduced automatically, if needed, so that the specified end timeis respected. This reduction does not occur if the analysis duration is set by the Number of Steps.

– The coupling step size is fixed for the duration of the System Coupling analysis, but it can be changedwhen restarting the analysis.

• Minimum Iterations

– This option allows specification of the fewest number of coupling iterations (at least 1) that could be ex-ecuted per coupling step.

– The specified minimum number of coupling iterations will be executed even if all measures of convergenceare realized in fewer iterations.

• Maximum Iterations

– This option allows specification of the greatest number of coupling iterations that could possibly be ex-ecuted per coupling step.

– The specified maximum number of coupling iterations may not be executed if the analysis convergesprior to the maximum iteration step being reached.




Analysis Settings Best Practices

This section provides information about best practices for the following analysis settings:General Analysis TypeTransient Analysis Type

General Analysis Type

With a General analysis type, accurate coupled solutions can be achieved using different combinationsof coupling step and coupling iteration specifications. The two cases described below are: when ananalysis is solved using one coupling step, and when an analysis is solved using many coupling steps.Your choice of the combination of coupling steps and coupling iterations will:

• determine when result and/or restart data is able to be written, as the restart points can only be writtenat the end of a coupling step,

• allow you to balance the required file storage space and your need for analysis restarts,

• determine how you can use system coupling’s under relaxation factor (see Under-Relaxation Al-gorithm (p. 54)) and ramping (see Ramping Algorithm (p. 53)), as these only apply to coupling iterationsand cannot be applied over coupling steps.

For more information about restarting your coupled analysis, see Restarting a System Coupling Analys-is (p. 35).

Coupled Analysis solved using only one Coupling Step

A coupled analysis can be solved using only one coupling step. In this case, the coupling step is madeup of many coupling iterations, and the solution is complete at the end of this one step. The analysiswill continue executing until either the solution converges, or the specified maximum number ofcoupling iterations is completed. Only the end of a coupling step can be used as a restart point. Whenonly one coupling step is used, results and restart data is generated only at the end of the solution.The analysis can be terminated as usual, but because intermediate restart data is not generated, thecoupled analysis cannot be restarted if it terminates abnormally (due to an error, power interruption,etc.) or if you terminate it before the coupling step is completed. Using only one coupling step withina coupled analysis minimizes file storage space at the expense of the ability to restart the analysis. In-terrupting the analysis will not affect the analysis, because System Coupling will complete the currentcoupling step (and so complete the solution) before stopping the analysis. Ramping and under-relaxationcan be applied across coupling iterations within the single coupling step.

Coupled Analysis solved using many Coupling Steps

A coupled analysis can be solved using many coupling steps. In this case, the coupling steps are madeup of one or more coupling iterations. The analysis will continue executing until the specified numberof coupling steps is completed. The transition from one coupling step to the next will occur when eitherthe solution converges or the specified maximum number of coupling iterations is completed. Only theend of a coupling step can be used as a restart point (you are able to specify which steps are used).Results and restart data is generated at the specified restart points. If the analysis should terminateabnormally within a coupling step, you can restart the analysis from the previous restart point. By usingmore coupling steps with fewer coupling iterations per step, as opposed to one coupling step withmany coupling iterations, more points at which restarts can be done are created. For difficult or complexanalyses, which might experience abnormal terminations, more restart points allow restarts of theanalysis (saving time and computational effort) at the expense of file storage space. System Coupling’sramping and under-relaxation can be used across coupling iterations, but cannot be used across



coupling steps, so System Coupling always transfers the full data transfer value at the end of eachcoupling step. Participant solvers may ramp data received from System Coupling at the coupling steps.

Transient Analysis Type

In a transient analysis, a coupling step is associated with a time interval by specifying the coupling stepsize (in seconds). With a time specified, a coupling step is the same as a time step within the transientanalysis. The coupling step size used should reflect the time scales of the physics being studied. Notethat unless sub-stepping is supported by the co-simulation participants being coupled, the couplingstep size will typically be limited by the finest/smallest time scale of the co-simulation participants. Ifthe analysis duration is specified using an End Time, then care should be taken to ensure that an integralnumber of coupling steps can be executed between the (re)start time and the specified end time. Ifthis is not done, then the final coupling step size will be reduced to respect the specified end time, andthis may introduce temporal discretization error into the coupled analysis.

The minimum number of coupling iterations may be set to a value larger than one (one is the default).If the data transfers have been under relaxed, you want to ensure a minimum number of coupling iter-ations is performed so that you iterate out the effect of the under-relaxation. Note that the data transferconvergence criteria would usually make this unnecessary.

The maximum number of coupling iterations should be set to allow complete convergence within eachcoupling step. Failure to fully converge within a given coupling step will modify the transient behaviorfrom that step onward.

Participants

You can connect a participant system's Setup cell to the System Coupling Setup cell in the projectschematic. The system coupling workspace displays a read-only summary of the participant data aftera refresh of the System Coupling Setup cell. The participant summary includes:

System nameThe name of the participant as presented in the schematic.

RegionsThe collection of regions from and to which data can be transferred. A region is most often a point, line,surface or volume that is part (or all) of the geometry or topology of a coupling participant. Note, however,that equations or probe (monitored) values may also be considered as point regions.

Note

System Coupling requires participants to use 3D meshes, with data transfer regionsconsisting of element faces from a 3D mesh. System Coupling data transfers cannot existin 2D meshes.




VariablesThe collection of input and output variables available for data transfer for each region. A variable is aphysical quantity such as force, length, or temperature that can be transferred between regions of participantsystems. Variables are defined as input or output variables for the specific region.

Note

For structural applications, data transfers are limited to force and displacement; forthermal heat transfer applications data transfers are limited to temperature, heat flow,heat transfer coefficient (also known as “convection coefficient”), and near wall temper-ature (also know as “bulk temperature” or “ambient temperature”).

Data Transfers

A data transfer is defined by one source and one target region, and is able to transfer one variable typein one direction between two participants.

Each data transfer is defined by a variety of properties such as Source, Target, and Data TransferControl. A one-way coupled analysis has data transfer(s) in only one direction between the coupledparticipants. In this type of analysis, the source region(s) are defined on only the participant sendingdata, and the target regions(s) are defined on only the participant whose solver is receiving the data.

A two-way coupled analysis has data transfers in both directions between the coupled participants. Inthis type of analysis, source and target regions are defined on both participants. For example, considera coupled two-way fluid-structure interaction analysis where a Fluent system and a Static Structuralsystem are the two participants. The Fluent system would have a region which is the source region forthe transfer of force, and the target region for the transfer of incremental displacement. The StaticStructural system would have a region that is the source region for the transfer of incremental displace-ment, and the target region for the transfer of force.

Source/TargetBoth Source and Target are each defined by a coupling participant along with a region and a variabledefined within the context of that participant. For a two-way data transfer on one region, you define twoindividual data transfers. When you set up your data transfers, a top-down approach should be followedwhen selecting Source and Target. Select in this order:

1. Source Participant

2. Source Region

3. Source Variable

4. Target Participant

5. Target Region

6. Target Variable

Data Transfer ControlAdditional properties can be defined to control the way in which the specified data transfers are executed.For each data transfer you can specify controls that determine:

• When the transfer is to occur.



• The under relaxation factor applied to the transfer.

• The convergence target.

• If ramping is used when applying data from the source-side to the target-side of the data transfer.

Transfer AtThe Transfer At property is used to control when the data transfer is executed by the solver. The onlyavailable option is:

Start of IterationTransfer data at the start of every coupling iteration within a coupling step.

Under Relaxation FactorThe factor multiplying the current data transfer values when under-relaxing them against the previousvalues. This is overridden with unity in the first coupling iteration of every coupling step only whenthe Analysis Type is Transient.

Note

When under-relaxation is used, there is no guarantee that the full value from thesource side of the data transfer is applied to the target by the end of the couplingstep.

RMS Convergence TargetThe target value used when evaluating convergence of the data transfer within a coupling iteration.The default value is 1e-2. The convergence target is RMS-based. For information regarding how thistarget is applied, see Evaluating Convergence of Data Transfers (p. 43).

RampingThe available options for ramping controlled by System Coupling are as follows:

NoneThe full data transfer value is applied to the target side of the interface for all coupling iterations.No ramping is the default option.

Linear to Minimum IterationsWithin each coupling step, the ramping factor is used to linearly increase the change in the datatransfer value applied to the target side of the interface. The data transfer value is increased duringeach coupling iteration until the specified minimum number of coupling iterations, , is reached.The ramping factor is applied to the change in the data transfer value from the previous couplingstep. If there is no change in this value from the last coupling step, the full data transfer value isapplied to the target side of the interface for all coupling iterations of that coupling step.

During the coupling iteration (for ), the ramping factor equals . The fulldata transfer value is applied for all coupling iterations that are equal to or greater than theminimum number of coupling iterations. As is always reached, the full data transfervalue is always applied by the end of each coupling step. This ramping behavior is demon-strated in Figure 3: Schematic of the Linear to Minimum Iterations Ramping Concept (p. 16)for the case where the minimum number of iterations specified is 5.

When ramping using Linear to Minimum Iterations, if the minimum number of iterations isthe same as the maximum number of iterations, then it is unlikely that the data transfer will




converge. It is a best practice for your maximum iterations to be larger than your minimumiterations.

Figure 3: Schematic of the Linear to Minimum Iterations Ramping Concept

Ramping and under-relaxation are independent operations. Ramping is applied before under-relaxation.

Note

System Coupling’s ramping will interact with ramping behaviors within the participant systems.To understand the full ramping behavior, verify ramping settings to see if your participantsystem is ramping loads received from System Coupling. For ramping behavior in Mechanical,see System Coupling Related Settings in Mechanical in the ANSYS Mechanical User's Guide.

See Working with Data Transfers (p. 16) for details about how to create, modify data transfers and doother common operations.

Working with Data Transfers

After you connect a participant system's Setup cell to the System Coupling Setup cell in the projectschematic, the System Coupling workspace displays the regions and variables available to create datatransfers after a Refresh of the Setup cell:

Create Data TransferThere are different ways to create single and multiple data transfers using the Create Data Transfer contextmenu option.

Create uninitialized data transferSelect the "Data Transfers" tree node in Outline view, then select Create Data Transfer from thecontext menu. This creates a new data transfer without any source or target properties defined. Youcan later modify the data transfer definition in Properties view.



Create data transfers for two regions from different participantsSelect two regions from different participants in the Outline view, then select Create Data Transferfrom the context menu. This creates multiple data transfers that vary based on the following criteria:

• Whether the two regions have the same topology

• Whether the input variable from one region has the same properties (such as the physical type) asthe output variable from the other region

Create data transfers for single regionSelect a region from a participant in the Outline view, then select Create Data Transfer from thecontext menu. This creates data transfers for each variable associated with the region. If the variableis an output variable, then the source participant, source region, and source variable are defined forthe new data transfer. If the variable is an input variable, then the target participant, target region, andtarget variable are defined for the new data transfer.

Create a data transfer for single variableSelect a region from a participant in Outline view, select a variable in the Properties view, then selectCreate Data Transfer from the context menu. This creates a new data transfer. If the selected variableis an output variable, then the source participant, source region, and source variable are defined forthe new data transfer. If the selected variable is an input variable, then the target participant, targetregion, and target variable is defined for the new data transfer.

Modify Data TransferSelect a data transfer in the Outline view. The Properties view displays all the properties for the datatransfer. You can modify all the properties for the data transfers in the same view.

Rename Data TransferSelect a data transfer in the Outline view. Double-click to rename the data transfer.

Duplicate Data TransferSelect one or more data transfers in the Outline view. Right-click and select Duplicate. This operationcreates new data transfers with the same Source, Target, and Data Transfer Control properties. Note thatyou can change these properties as needed for these new data transfers.

Suppress Data TransferSelect one or more data transfers in the Outline view. Right-click and select Suppress to prevent the datatransfer.

Delete Data TransferSelect one or more data transfers in the Outline view. Right-click and select Delete to remove them.

Note

If the data transfer definition is not valid or the data is invalidated for any reason, the stateof the node will show as a ? and the incorrect properties will need to be changed.




Data Transfer Rules

When you create data transfers in System Coupling, certain rules must be observed in order to correctlydefine the analysis.

Note

Participant data transfer regions must consist of triangular or quadrilateral faces. Polyhedralfaces as well as faces with hanging nodes (cut-cells) are not supported in System Coupling.

Currently, the following three types of transfers are supported. Details of these three types of transfersare given in Table 2: Data Transfers available in System Coupling (p. 18).

• Force transfers

• Motion transfers

• Thermal transfers

Force and motion transfers are typical for fluid-structure interaction problems, where a load to thestructure is transferred from a fluid solver, and the deformations to the fluid are transferred from thestructural solver. There can only be one force transfer and one motion transfer for each data transferregion.

Thermal transfers can be transferred between ANSYS Fluent and ANSYS Mechanical directly throughSystem Coupling, or through the coupling of the External Data system. Three thermal transfers areavailable, each transferring different thermal variables. The three thermal transfers are described in thetable below.

For one-way thermal transfers, only one of the three options below for thermal transfers can be definedfor a given pair of source and target regions.

For two-way thermal transfers, two data transfers are set up on the same data transfer region. In a two-way transfer:

• the two variables, heat transfer coefficient and near wall temperature, cannot be transferred on thesame data transfer region as heat flow, and

• a participant’s data transfer region cannot provide and receive the same thermal variable(s); for example,Fluent cannot send and receive temperature data on the same data transfer region.

Table 2: Data Transfers available in System Coupling

Data TransferDirection

Variable(s) TransferredTransfer Type

Force transfer •• from a fluid solver toa structural solver

Force (VectorXYZ*)

Motion transfer** •• from a structuralsolver to a fluid solver

Incremental displacement(VectorXYZ*)



Data TransferDirection

Variable(s) TransferredTransfer Type

1.Temperaturetransfer

ThermalDataTransfers

• from a structuralsolver to a fluidsolver, or

• Temperature (Scalar)

• from a fluid solver toa structural solver

2. Heat flowtransfer

• from a structuralsolver to a fluidsolver, or

• Heat flow (also known asheat rate) (Scalar)

• from a fluid solver toa structural solver

3. A pair ofvariables***

•• Heat transfer coefficient(also known as convectioncoefficient)** (Scalar)

from a fluid solver toa structural solver

• Near wall temperature (alsoknown as bulktemperature, or ambienttemperature)** (Scalar)

* Represents the force vector ( , , ) and the incremental displacements vector ( , , )respectively.

**In a general coupled analysis, when the solver receiving the motion (such as Fluent) solves before orsimultaneously to the solver sending the motion (such as Mechanical), then the incremental displacementtransferred during the first coupling iteration of each coupling step is identically zero. This behaviorcan be changed by using GeneralAnalysis_IncrDisp_InitIterationValue_Zero in theExpert Settings (p. 24).

***You must correctly define both variables in the data transfer in order for this thermal transfer to bevalid.

Note

For a given target region, there can only be one source region. However, a given source regioncan send data to multiple target regions. In other words, 1-to-M data transfers are supported,where M is an integer and is greater than or equal to 1. Note that M-to-1 data transfers arenot supported.

Execution Control

Execution Control has the following capabilities:Co-Simulation Participant SequencingDebug Output ControlIntermediate Restart Data Output




Co-Simulation Participant Sequencing

The System Coupling system offers comprehensive control over the sequencing of co-simulation parti-cipants, and specifically over the data transfers that are required to obtain a solution. This is controlledthrough the settings in the Co-Sim Sequence. The participants are sequenced by assigning a sequencevalue, which is an integer value between 1 and the number of participants in the analysis, to eachparticipant. Each participant executes its solutions (that is, all required data transfers, followed by ob-taining the equation solution) in the order of its sequence value, where the participants with the lowersequence values execute first. The coupled analysis will use sequential solutions or simultaneous solutions,depending on the assigned sequence values. This is described in more detail below.

Note

To improve solution stability, sequential solutions are used by default. Note as well that,to facilitate synchronization of interface geometry, participants that consume geomet-rical or mesh deformations (for example, the Fluids solver in a Fluid Structure Interactionanalysis) are automatically assigned larger sequence values by default.

Additional information can also be found in Best Practice Guidelines for Using System Coupling (p. 73).

Sequential Solutions

A sequential solution is done when all co-simulation participants are assigned different solution sequencevalues. In particular, participants perform their solutions (that is, all required data transfers, followed byobtaining the equation solution) in the order of the sequence values specified in the user interface.Sequential solutions are optimal for analyses that involve strong physical couplings, because the mostrecent information from one participant is always used by subsequent participants. This typicallytranslates into requiring the fewest coupling iteration per coupling step to reach a converged solution.However, it may not yield the shortest (wall-clock) solution time if the participants are run on differentCPUs.

Simultaneous Solutions

A simultaneous solution is done when one or more co-simulation participants are assigned identicalsolution sequence values. In particular, when the same sequence value is applied to multiple participants,then all those participants perform their respective data transfers, after which those same participantsperform their equation solutions simultaneously.

Simultaneous solutions are optimal for analyses that involve weak physical couplings because the mostrecent information from one co-simulation participant is not required by other simultaneously executedparticipants in order to reach a converged solution. Additionally, the overall (wall-clock) solution timemay be reduced if the simultaneously executed participants are run on different CPUs. However, if usedwith co-simulation participants that exhibit strong physical couplings, simultaneous solutions may ad-versely affect the rate of convergence, and possibly lead to divergence.

Debug Output Control

The Debug Output entity under Execution Control in the outline model controls the level of debuginformation written in the System Coupling Log (*.scl) file during the execution of the solution. Thebasic level of detail included is controlled using one of the following levels:

• None



• Level 1

• Level 2

• Level 3

• Level 4

• All Levels

By default, the value set for the Global Level is applied to all stages of solution execution listed below.To use a different value for one or more of the specific stages of solution execution, change the valuefrom Use Global Level to the desired output level.

Note that stages of solution execution that are associated with Data Transfers are grouped together,and have their own default Data Transfers Level value. To use a different value for one or more ofthese stages of solution execution, change the value from Use Data Transfers Level to the desiredoutput level.

The following properties control the debug level for different sections of the log:

StartupControls the level of output from the start of the coupling service until creation of the "Summary of SCSetup" banner in the SCL file.

Participant ConnectionControls the level of output from the end of the setup validation until the Initial Synchronization syn-chronization point (that is, between the Setup Validation and System Coupling Summary banners).

Analysis InitializationControls the level of output from the end of the setup validation until the Analysis Initialization synchron-ization point (that is, between the System Coupling Summary and Solution banners).

Solution InitializationControls the level of output during the setup of coupling steps and coupling iterations. This output doesnot include information related to the data transfers.

Data TransfersSpecifies the debug output generated for data transfers. Note that header information for mapping isgenerated whenever the mesh coordinate or mesh topology output is requested. Similarly, header inform-ation for the data transfers is generated whenever the transfer data output is requested.

Data Transfers LevelProvides the default level for the different debug output controls in the Data Transfers group. If thedebug level of any property in the Data Transfers group is set to Default, then the debug level ofthat entry is governed by the level set here. If the Data Transfers Level itself is set to Use GlobalLevel, then it derives its value from the default level defined for all debug output controls.

Source Mesh CoordinatesControls the level of output for mesh coordinates of the source region in all data transfers.

Source Mesh TopologyControls the level of output for mesh topology (elements and nodes) of the source region in all datatransfers.




Source DataControls the level of output for the source data in all data transfers.

Target Mesh CoordinatesControls the level of output for mesh coordinates of the source region in all data transfers.

Target Mesh TopologyControls the level of output for mesh topology (elements and nodes) of the source region in all datatransfers.

Target DataControls the level of output for the target data in all data transfers.

Convergence ChecksControls the level of output from the Check Convergence synchronization point until the next synchron-ization point, which may be either Shutdown or Solution.

ShutdownControls the level of output after the Shutdown synchronization point.

For information about synchronization points, see Process Synchronization and Analysis Evolution (p. 41).

Note

The debug level for all the properties, except Default, can be set at any level. For the Defaultproperty, the available levels are from None to All Levels. Increasing levels always generatemore detailed output. Note, as well, that the output level settings for each of the mesh co-ordinates, topology, and transfer data, control the number of lines of output generated.

Specifically, 10L lines of data will be written for an output level setting of L (for example, 100lines will be written for an output level of 2, or Level 2).

Intermediate Restart Data Output

The Intermediate Restart Data Output entity under Execution Control in the outline model allowsthe selection of time points at which restart data should be generated during the execution of thesolution. Depending on the participant, the restart data may or may not be the same as the resultsdata. Writing of results data for post-processing should be set from within the participant setup cell.

Important

During execution of the coupled analysis, co-simulation participants will automatically berequested to generate intermediate restart data at the same frequency as the SystemCoupling service. Note that this feature only affects the frequency at which data is generated;the content of data is determined by the participant. To see if this feature is supported, seeSupported System Couplings (p. 3).

Choose one of the following options to control when restart data is produced.

NoneNo intermediate restart output files are generated using this option. This option is enabled by default.



All stepsRestart output files are generated at the end of each coupling step.

At Step IntervalRestart output files are generated at the end of the coupling steps corresponding to the interval specifiedin the Step Interval box below.

Note

If you specify a Step Interval that is above or below the allowed limit, an error is dis-played; change the Step Interval as required.

Validation and State of the System Coupling Setup Cell

Validation of the Setup cell depends upon the validation of the individual nodes in the Tree View (forexample, Analysis Settings and Data Transfer). If any of these nodes is invalid, it would be markedby a ? (Attention Required) in front of the Setup cell. Details regarding why validation failed arepresented when the mouse pointer is hovered over the ? symbol.

System Coupling Setup Cell Context Menus

The System Coupling Setup cell has several context menus:

• Start/Stop highlighting linked nodes: From the Setup cell, this option controls whether cells that are relatedto the selected cell are highlighted in the Outline view.

• Create Data Transfer: From Data Transfers you can create one or more data transfers using this contextmenu. See Working with Data Transfers (p. 16) for details.

• Auto Show/Hide

• Toolbar Option

• Rename: From Data Transfers you can rename the selected data transfers using this context menu. SeeWorking with Data Transfers (p. 16) for details.

• Duplicate: From Data Transfers you can duplicate the selected data transfers using this context menu. SeeWorking with Data Transfers (p. 16) for details.

• Display Validation Failure: Select this to display error messages when System Coupling setup settings arefound to be incorrect due to validation problems.

• Add Property: From Execution Control>Expert Settings, you can add specific expert settings. See ExpertSettings (p. 24) for details about these settings.

• Remove Property: From Execution Control>Expert Settings, you can remove specific expert settings. SeeExpert Settings (p. 24) for details about these settings.

• Read restart points: From Properties of Analysis Settings>Initialization Controls>Coupling Initialization,you can use this command to populate the list of restart points. This command is useful for abnormal situationssuch as a workbench crash. In such situations, the restart point list may be empty even though the interme-diate restart files exist on your disk. Read restart points is used to repopulate your list of restart points, sothat you can restart from a previously saved restart point.




See Understanding Cell States in the Workbench User’s Guide for detailed information on typical cellstates.

Expert Settings

This subsection is used to specify the expert settings that are available. Expert settings provide youwith additional advanced controls for many of the settings available in the Outline and Propertiesviews under the Setup branch.

• General Expert Settings

– DumpInterfaceMeshes (string)

The only valid value for this setting is CFDPost. When this expert setting is used, files named<Name of Data Transfer>source.csv or <Name of Data Transfer>target.csvare generated during the mapping process. These files report values of 0 and 1 for unmapped andmapped nodes, respectively. These files are appropriate for import into CFD-Post as user definedsurfaces for the visualization of mapping data.

– MeshSyncOption (integer)

Value is 0, 1, 2, or 3 (default: 0). This setting is only relevant for coupled analyses with a participantthat consumes geometric data (for example, the Fluids solver in a Fluid Structure Interaction ana-lysis, which receives displacement data). This setting can be used when the solution of the participantconsuming geometrical data is either sequenced identically as, or sequenced before, the solutionof the participant that provides the geometric data. Available options are:

→ 0 (default): If the maximum number of coupling iterations per coupling step is 1, then the solutionsequence is changed so that the participant that consumes geometrical data is solved last. If themaximum number of coupling iterations per coupling step is greater than 1, then one additionalcoupling iteration is performed at the end of the coupling step and only the participant thatconsumes geometrical data is re-solved.

→ 1: Regardless of the maximum number of coupling iterations per coupling step, the solutionsequence is changed so that within each coupling iteration, the participant that consumes geo-metrical data is solved last.

→ 2: Regardless of the maximum number of coupling iterations per coupling step, one additionalcoupling iteration is performed at the end of the coupling step and only the participant thatconsumes geometrical data is re-solved.

→ 3: No setup modifications are applied, and the solution proceeds with the specified participantsequencing.

– GeneralAnalysis_IncrDisp_InitIterationValue_Zero (integer)

Value is 0 or 1 (default: 1). This setting is only relevant in a general coupled analysis, when displace-ment is transferred, and when the solver receiving the displacement (such as Fluent) solves beforeor simultaneously to the solver sending the displacement data (such as Mechanical).

→ 1: During the first coupling iteration of each coupling step the displacement transferred to the targetis 0 [m] (irrespective of the value provided by the source). This override of the transfer value is to avoidpossible double displacement, which could create folding of the mesh.



→ 0: The value for displacement provided by the source is transferred with no interference by this expertsetting (this value transferred may be modified by other settings such as ramping).

• Participant Variable Initial Value Settings

The following expert settings are useful for overriding the default initial values of variables of a giventype for all participants. These initial values are currently used in the ramping as well as the under-relaxation of data transfers. Note that for the ramping algorithm, the reference target-side value fordisplacement is always 0.0 [m]. The expert settings below will have no effect on the value used inthis case.

– Participant_Variable_InitValue_IncrDisp_X (real)

Participant_Variable_InitValue_IncrDisp_Y (real)

Participant_Variable_InitValue_IncrDisp_Z (real)

Replace initial value for Cartesian components of all variables of type "Incremental Displacement"for all coupling participants. Default is 0.0 [m].

– Participant_Variable_InitValue_Force_X (real)

Participant_Variable_InitValue_Force_Y (real)

Participant_Variable_InitValue_Force_Z (real)

Replace initial value for Cartesian components of all variables of type "Force" for all coupling parti-cipants. Default is 0.0 [N].

– Participant_Variable_InitValue_Temperature (real)

Replace initial value for all variables of type "Temperature" for all coupling participants (variablesinclude temperature and near wall temperature). Default is 295.15 [K].

– Participant_Variable_InitValue_HeatRate (real)

Replace initial value for all variables of type "Heat Rate" for all coupling participants. Default is 0.0[W].

– Participant_Variable_InitValue_HeatTransferCoef (real)

Replace initial value for all variables of type "Heat Transfer Coefficient" for all coupling participants.Default is 0.0 [W m^-2 K^-1].

• Data Transfer Control Settings

The following expert settings are useful for controlling the behavior of data transfers.

– DataTransfer_ScaleFactor_Force (double)

Scale, by the factor specified, source values for all data transfers of Force variables. Default valueis 1.0.

– DataTransfer_ScaleFactor_HeatRate (double)




Scale, by the factor specified, source values for all data transfers of Heat Rate variables. Defaultvalue is 1.0.

– DataTransfer_ScaleFactor_HeatTransferCoef (double)

Scale, by the factor specified, source values for all data transfers of Heat Transfer Coefficient variables.Default value is 1.0.

– DataTransfer_ScaleFactor_IncrDisp (double)

Scale, by the factor specified, source values for all data transfers of Incremental Displacementvariables. Default value is 1.0.

– DataTransfer_ScaleFactor_Temperature (double)

Scale, by the factor specified, source values for all data transfers of Temperature variables. Defaultvalue is 1.0.

• SC Log Output Control Settings

The following expert settings are useful for controlling the output of various supplemental diagnosticsto the SC log file:

– DTDiagShowRMSChange (string)

Activates reporting of RMS change in data transfers if set to true. Default is ‘False’.

When RMS change is the type of data checked against the convergence target (this is the default),this expert setting does nothing.

– DTDiagShowMaxChange (string)

Activates reporting of Max change in data transfers if set to true. Default is ‘False’.

If Max change is the type of data checked against the convergence target, this expert setting doesnothing. Note that the type of data checked (RMS change or Max change) can only be changedthrough the System Coupling Input File.

– DTDiagShowMinValue (string)

Activates reporting of minimum nodal value in data transfers if set to true. Default is ‘False’.

– DTDiagShowMaxValue (string)

Activates reporting of maximum nodal value in data transfers if set to true. Default is ‘False’.

– DTDiagShowAvgValue (string)

Activates reporting of average nodal value in data transfers if set to true. Default is ‘False’.

– DTDiagShowSum (string)

Activates reporting of sum of nodal values in data transfers if set to true. Default is ‘False’.

– DTDiagShowAll (string)



Activates reporting of all diagnostics of nodal values in data transfers if set to true. Default is ‘False’.

• Expert Settings Related to Mapping

The coupling service uses a Profile Preserving mapping (ProfMap) for non-conservative quantities (forexample, displacement) data transfers, and a Conservative mapping (ConsMap) for conservativequantities (for example, forces).

– ProfMapBucketScale (integer)

Value (ranging from 0 to 100, default: 50) that represents the number of discrete search ‘buckets’,as a percentage of the number of nodes, to use during mapping. The objective is to generate‘buckets’ that will contain roughly equal numbers of nodes. This setting will affect the speed ofthe mapping, but it should not affect the outcome.

– ProfMapBucketTol (double)

Value (ranging from 0 to 1, default: 1e-4) that is used to create a bounding region around eachtarget node. The bounding region is used to increase the number of buckets that will be includedin the Bucket Surface Algorithm's search, which in some cases will improve the number of mappednodes.

– ProfMapEdgeTol (double)

Value (ranging from 0 to 1, default: 0.05 in natural coordinate space) that specifies the tolerancewithin which a target node may be found in a source element. See the discussion on Bucket Sur-face (p. 48) mapping algorithm in the section Mapping Algorithms (p. 46) for more informationregarding this tolerance setting.

– ProfMapTolOption (integer)

Value is either 0 or 1 (default: 0), where 0 indicates that the specified tolerance is relative to themaximum Cartesian extent of the region being mapped, and 1 indicates that the specified toleranceis absolute (using the same units as the mesh coordinates).

– ProfMapTol (double)

Value (ranging from 0 to 1, default: 1e-6) that specifies the tolerance for the 'gap' distance betweena target node and the source element that it is mapped to.

– ProfMapEnforceTol (integer)

Value is either 0 or 1 (default: 0), where 0 indicates that the distance between a target node andthe source element that it is mapped to (also known as the ‘gap’ distance) is not checked againstthe tolerance specified with the expert setting ProfMapTol. Target nodes with final ‘gap’ distanceslarger than the specified tolerance will be reported as mapped in the SCL file. These nodes aremapped to the source nodes like all of the other mapped nodes and given a value accordingly.

A setting of 1 (which means on) indicates that such a check is performed. Target nodes with final‘gap’ distances larger than the specified tolerance will be reported as unmapped in the SCL file.These nodes are mapped to the source nodes like all of the other mapped nodes and given a valueaccordingly.

– ConsMapPixelRes (integer)




Value, (ranging from 10 to 256, default: 100), that indicates the number of pixels to use whenforming the surfaces of intersection for each pair of source and target mesh element faces on theinterface. Larger values are needed if interface mesh lines are very nearly coincident. Any valueentered that is less than 10 or greater than 256 will be reset to 100 automatically.

– ConsMapTol (double)

Value, (ranging from 0.1 and 1, default: 0.1), that specifies the tolerance, in the element-face-normaldirection, to use when determining whether the source and target meshes map to one another.This tolerance is normalized by the local element size. Any value entered that is less than 0.1 orgreater than 1 will be reset to 0.1 automatically.

Settings for Running a System Coupling Solution

This section describes:

• All the settings that appear in the Outline and Properties views under the “Solution” branch.

• Context menus (that is, the menus that appear with a right-click) for the Solution cell.

See the following sections for additional information:Solution InformationSystem Coupling ChartValidation and State of the System Coupling Solution CellSystem Coupling Solution Cell Context Menus

Solution Information

Solution information is automatically generated for output of the system coupling service and thecoupling participants. Figure 4: An Example of the Solution Information Branch (p. 29) displays an exampleof the “Solution Information” branch from the Outline view. Select an entry from the listed solutioninformation sources to display its output in the Solution Information view.

Note

The default behavior of the Solution Information view is to always show the latest inform-ation in the log file. Each time new information is added, the file will automatically scroll tothe end. However, if you move the vertical scroll bar away from the bottom, the view willnot scroll to the end when new information is added until you move the scroll bar back tothe end.

There are also some keyboard short-cuts that are available when operating in this view:

• Page Up scrolls up one page.

• Page Down scrolls down one page.

• Ctrl+Home jumps to the top of the log.

• Ctrl+End jumps to the bottom of the log.



Figure 4: An Example of the Solution Information Branch

For additional details about the solution information displayed for the coupling service, see SystemCoupling Service Log File (scLog.scl_, scLog_##.scl) (p. 57). For additional details aboutsolution information displayed for coupling participants, see Supported System Couplings (p. 3).

System Coupling Chart

System Coupling's chart monitor allows you plot data produced during the coupled solution process.You can use this data to monitor convergence. The chart monitors can plot data from the systemcoupling execution and from the coupling participants, such as Fluent.

Convergence data is available for plotting once the solution is running or has been completed. You cancreate multiple charts (p. 30), and select the variables (p. 30) that you want to plot.

In the chart monitor, data is available for plotting against different levels (X axis data). The higher(coarser) levels at which the data is present are referred to as parent levels, whereas the lower (finer)levels at which the data is present are referred to as child levels. Any data present in a child level arealso available at the parent level for plotting. For example: In the graphic that follows, the flow chartshows different variables and levels for a sample run. "Coupling Step" is the parent level for "CouplingIteration", whereas "Solver 1 Step", "Solver 1 Iteration", "Solver 2 Step", and "Solver 2 Iteration" are childlevels of "Coupling Iteration". There are two variables, "Variable 1" and "Variable 2", present. "Variable1" is present at "Solver 1 Iteration" and hence is available for plotting at "Solver 1 Iteration" or any ofits parents, that is, "Solver 1 Step", "Coupling Iteration" or "Coupling Step". Similarly, "Variable 2" isavailable for plotting at "Solver 2 Iteration", "Solver 2 Step", "Coupling Iteration", and "Coupling Step".

Chart Properties

Axis X Property:

• Quantity: The level at which the X data for the variables is plotted. This can be any level at which thedata is available. For example: For a variable "Data Transfer:Change:RMS", the available levels can be




"Coupling Step" and "Coupling Iteration". The X axis level can be defined by selecting an option in thedrop-down options list in the Properties view of a chart.

Axis Y Property:

• Title: The title of the axis

Properties Supported for Both Axes:

• Scale: The scale of the axis. Scale can be defined as Linear, Common Log (Log base 10) or Natural Log.

• Automatic Range: The property to define whether or not automatic scaling should be applied to theaxis, or whether the RangeMin and RangeMax should be used.

• Range Minimum: The minimum range of the values in this axis.

• Range Maximum: The maximum range of the values in this axis.

Chart Variable

The System Coupling Chart Monitor plots data produced during the coupled solution process. Thesevariables that you can plot are organized according to coupling participants and include:

• measures of convergence obtained from co-simulation participants (for example, solver residuals from Fluent)

• the change (RMS or maximum) in data transfer values

• diagnostic values (for example, minimum, maximum, average, and sum) taken from the nodal data associatedwith data transfers

The variables that are obtained from co-simulation participants are only plotted at the intervals thatthey are available. Intermediate data points are not artificially created.

Chart Variable Properties

Refinement LevelThe data plotted at the level defined by the X axis can be further refined to any of the child levels of theX axis. For example: For X axis level defined at the "Coupling Step", the X data values for a variable can berefined to the "Coupling Iteration" level. In this case the intermediate values available at "Coupling Iteration"level between consecutive "Coupling Steps" are distributed equally between the coupling steps; that is,if "Coupling Step" 2 has three "Coupling Iterations", then the data points are plotted at 1.33, 1.66, and 2.The refinement level can be defined by selecting an option in the drop down options list in the Propertiesview of a chart.

Style

• Color: The line color of the chart variable in a plot

• Line Width: The width of the line drawn for this chart variable in pixels

• Symbol Size: The size of a symbol in pixels when a symbol is drawn for this variable

Working with System Coupling Charts

The following context menu options are available:



Create ChartYou can create convergence charts by using the Create Chart context menu option. In the Outline view,right-click Chart Monitors, then select Create Chart from the context menu. This creates a new systemcoupling chart without any variables defined. The default X axis level is "Coupling Iteration".

Add VariableOnce the solution is running or completed, variables to be plotted can be added to a system couplingchart. Select an existing chart in the Outline view, and then select Add Variable from the context menu.From this context menu, select data of interest to add it to the chart. The default refinement level for theadded variable is set to the X axis level. If the data for the new variable is not available at the level definedby the X axis, the X axis level and the refinement level for the new variable are set to "Coupling Iteration".

Remove VariableSelect a variable under the Remove Variable context menu option to remove that variable from the chart.

Delete VariableA variable included in the chart can be removed using the Delete context menu option.

DeleteSelect Delete in the chart’s context menu to delete the chart.

Editing Chart and Chart Variable PropertiesChart and Chart Variable properties are displayed and can be edited in Properties view based on selectionin Outline view.

Note

When the solution is started, a default chart is added if one is not already present. The defaultvariables added correspond to the RMS Change in data on the target side of all data transfers.For example if "Data Transfer" and "Data Transfer 2" are defined with target participantsequal to "Transient Structural" and "Fluid Flow", respectively, then the chart variables "Tran-sient Structural: Data Transfer: Change: RMS" and "Fluid Flow: Data Transfer 2: Change: RMS"are added to the default chart. If you add/delete variables to the default chart, then newvariables are not added by default on consecutive runs.

Using the System Coupling Chart View

Chart Zoom, Pan, and FitYou can manipulate the display of a chart using the zoom, pan, and fit features.

• Zoom by using the mouse wheel or Shift+middle mouse button

• Box zoom by using the right mouse button

• Pan by using Ctrl+middle mouse button

• Fit by using the F key.

Saving a ChartYou can save the chart that you are viewing as a graphic. To do so, right-click the background of the chartand select Save Image As. In the dialog box that appears, you will see a small image of the chart, and can

select the Size (resolution) that will be used when saving the chart. Click the button and navigate tothe folder where you want to save the file. Enter a file name. You can select either .png or .bmp as the




graphic file type. Click Save to select that file path as your save location. Click OK to save the file to thelocation that you selected, with the resolution that you have selected.

Validation and State of the System Coupling Solution Cell

The state of the Solution cell is coupled to the states of the Solution cells for all co-simulation participants.In particular, all coupled Solution cells will have the same state, which will reflect the least completestate of all coupled cells.

System Coupling Solution Cell Context Menus

The System Coupling Solution cell has several context menus:

• From the Solution cell, right-click and you can:

– Update the solution,

– Continue Calculation if the solution was interrupted,

– Refresh the solution,

– Clear Generated Data,

– Reset the solution.

These commands are the same as those available on the System Coupling’s Solution cell in the ProjectSchematic.

• From the Solution > Chart Monitor cell, right-click and select Create Chart to create a system couplingchart.

• From the Solution > Chart Monitor > Chart cell, right-click and select Add/Remove Variable to add orremove variables from the selected chart. For details, see Working with System Coupling Charts (p. 30).

• Display Validation Failure: Select this to display error messages when System Coupling solution items (forexample, charts) are found to be incorrect due to validation problems.

Note

If a coupled analysis is interrupted before reaching the specified coupling duration, then theSolution cells will remain in an ‘Update Required’ state once execution stops, because thecalculation needs to be continued to complete the analysis. Downstream Results cells maybe refreshed and/or updated to review the results generated up to the point at which theanalysis was interrupted.

See Understanding Cell States in the Workbench User’s Guide for detailed information on typical cellstates.



Workflows for System Coupling

This chapter describes general issues common to working with System Coupling systems.Executing System Couplings Using the Command LineRestarting a System Coupling AnalysisStopping the Coupled Analysis Run

Executing System Couplings Using the Command Line

You can set up system coupling simulations by using the command line, rather than by using theWorkbench user interface.

To perform a system coupling simulation from the command line, you need to ensure paths to all requiredscripts and executables are added to the PATH environment variable so that these applications can belaunched from command line.

Tip

Search your installation to help resolve any missing dynamic libraries.

To run an analysis from the command line, execute the steps below. If you would like an example ofthis process, the tutorial Oscillating Plate with Two-Way Fluid-Structure Interaction provides detailedsteps on how to use the Command Line in the section Executing the Coupled Analysis from the CommandLine.

1. Generate the System Coupling Input file and place this file in the desired working directory for theCoupling Service. To do this, enter (double click) the System Coupling Setup cell in the Workbenchschematic, and select the Export SCI File option from the File menu. Note that this option is only availablewhen the state of the Setup cell is up-to-date.

2. Generate all input files required for the co-simulation participants (that is, input files required for thesolvers involved in the coupling) and place these files in the respective desired working directories.

3. The command to start the Coupling Service differs between Linux and Windows:

• Linux:

.workbench -cmd ansys.services.systemcoupling.exe -inputFile oscillating_plate.sci

where .workbench is a script located in /ansys_inc/v160/aisol on Linux.

The typical location of the executable on Linux 64-bit Workbench installations is:

/ansys_inc/v160/aisol/CommonFiles/linx64

• Windows:

ansys.services.systemcoupling.exe -inputFile oscillating_plate.sci



The typical location of the executable on Windows 64-bit Workbench installations is:

C:~\ANSYS Inc\v160\aisol\bin\winx64

These commands launch the Coupling Service and create a System Coupling Server file (scServ-er.scs) in the working directory. As described in System Coupling Server File (scServ-er.scs) (p. 56), this file contains information needed to start each of the co-simulation participants,specifically port and host information for the coupling service and identifiers for the participants.

Additional information needed to run from the command line is accessible below for each of theco-simulation participants that support system couplings.

For more information about command line execution and options for supported co-simulation parti-cipants, see Supported System Couplings (p. 3). Co-simulation participants will tend to use a commonset of system coupling related command line options (such as -schost, -scport, and -scname).You are strongly encouraged, however, to develop some expertise in running each of the participantswithout system couplings before attempting to execute coupled analyses from the command line.

Additional system coupling command line information can also be found in the following section:System Coupling Command Line Options

System Coupling Command Line Options

The following command-line options are available in the command line:

-debugLevel [ 0 | 1 | 2 | 3 | 4 | 5 ]Generates debug output to the System Coupling Log (.scl) file. The level of debug output increases witheach level, with the default (0) providing no debug output and level 5 providing the most complete debugoutput.

-extractInputFile input_file_nameExtracts the content of an identified System Coupling Input (scInput.sci) file that is contained in thespecified System Coupling Results (scResults_##_######.scr) file (via -resultFile). Valid namesare the ones returned by the -listInputFiles command line option.

-helpDisplays the option summary.

-inputFile path_to_sci_fileInputs to the coupled analysis are extracted from the specified System Coupling Input file, wherepath_to_sci_file is the location of the input file.

-listInputFilesLists all of the input files stored in the specified System Coupling Results file (via -resultFile). Outputis written to the System Coupling Log file for the run.

-logFile path_to_scl_fileGenerates the System Coupling Log file with a specific name in a specific directory, wherepath_to_scl_file is the location of the generated log file. The default log file name is scLog.scland will be generated in the same directory from which the coupling services executable is run.



-resultFile path_to_scr_fileContinue the analysis from the specified System Coupling Results file, where path_to_scr_file is thelocation of the results file. Note that if the -inputFile option is also used, then inputs to the coupledanalysis are extracted from that file.

For more information about command line execution and options for supported co-simulation parti-cipants, see Supported System Couplings (p. 3).

Restarting a System Coupling Analysis

The sections below walks you through the steps needed to restart a coupled analysis using SystemCoupling, but you will also need restart information specific to the participants connected to your SystemCoupling system. See Supported System Couplings for a list of supported systems and references totheir corresponding documentation regarding restarts.

Restarting a coupled analysis is further described in the following sections:Generating Restart FilesExecuting the Restart RunRecovering from a Workbench Crash

Note

• The System Coupling Results file generated by the coupling service contains all the informationand data that are required to restart the coupling service only. Information and data that are re-quired to restart the coupling participants, as well as the act of restarting those participants, aremanaged by the participants themselves.

• The convergence history for a restarted run is generally not identical to that observed in a con-tinuous run. There are two factors contributing to changes in convergence: interfaces are re-mapped upon restart, thereby changing the interpolation weights; and restart- and continuous-run convergence histories are not always identical (for example, the HHT transient discretizationused by ANSYS Mechanical will not yield identical convergence histories while the Newmarkdiscretization will).

• Changes in convergence history across restarts will yield changes in solution values if solutionsare not fully converged within coupling steps.

Generating Restart Files

Restarts of a system coupling analysis requires corresponding restart points to exist in the couplingservice and in each of the solvers participating in the analysis.

During a coupled analysis, restart points that contain information for restarts need to be created by allof the systems involved in your coupled analysis. System Coupling’s restart file is the System CouplingResults (scr) file. Creation of restart points is controlled in System Coupling to ensure participant solversare writing data at synchronized coupling steps.

To generate restart files for a coupled analysis, follow the steps below:

1. Before starting the analysis’ initial run, ensure that all coupling participants are set up to save (or retain)the corresponding restart points during the run. For information on how to do this, see Supported System




Couplings for a list of supported systems and references to their corresponding documentation regardingrestarts.

2. Set up the System Coupling system to control the creation of restart points at certain intervals during thecoupled analysis run.

a. From the Project Schematic, double-click System Coupling's Setup cell to open the System Couplingtab.

b. In System Coupling's Outline view on the left, select System Coupling > Setup > Execution Control> Intermediate Restart Data Output.

c. In the Properties view, under Output Frequency, select the appropriate setting. See IntermediateRestart Data Output for more information.

Executing the Restart Run

Once the coupled analysis run is finished or interrupted, or if the solution fails, you can restart this runfrom any of the saved restart points. You need to select the same restart point in all coupling participants,as well as in the System Coupling system.

To execute the restart run:

1. Specify a restart point in each participant connected to System Coupling. Make sure that these restartpoints correspond to the restart point you will choose in System Coupling.

For information on how to do this for participant systems in your coupled analysis, see SupportedSystem Couplings for a list of supported systems and references to their corresponding restartdocumentation.

2. If setup changes in the participant systems are needed before restarting, make these required changes.


3. In some cases, setup changes are desired or are required to avoid failure of the coupled analysis. To makethese changes:

a. Double-click the System Coupling Setup cell or Solution cell to open the System Coupling tab.

b. Modify the required settings in System Coupling. Setup changes commonly include changes to acombination of the following:

• Coupling analysis type

• Coupling initialization and duration settings

• Coupling step size

• Minimum and maximum number of coupling iterations per coupling step

• Data transfer convergence targets and under-relaxation factors



If running your analysis from the command line, note that each of the –inputFile and –res-ultFile command line options are required for this type of restart. If no modifications weremade, only the –resultFile command line option is required for the restart.

4. Select the restart point for the System Coupling system. To do this:

a. If the System Coupling tab is not already open, double-click the System Coupling Setup cell orSolution cell to open the System Coupling tab.

b. In the System Coupling tab, select Analysis Settings, then in Properties of Analysis Settings >Coupling Initialization, pick a restart point that corresponds to the restart point you selected in theparticipant systems.

5. Start your restart run. To do this, in the System Coupling tab, right-click Solution and select Update. Yourrestarted coupled analysis will now begin to solve.

Recovering from a Workbench Crash

Workbench or one of the components may crash such that restart files are available but they are notrecognized or populated in the Workbench project. If this is the case, you will be able to recover yourproject and restart your analysis using the steps below.

The usual project directory (ProjectName_files) contains the latest System Coupling results andrestart points (these solvers use the live project instead of running in a temporary directory).

Note that the .backup directory contains the original version of any files which have been modifiedsince the last save. These files are useful to recover the last saved state, but they are not useful for re-starting your analysis.

To recover the project to be able to restart from a restart point:

1. Launch Workbench and open the project. Since the project was not closed down cleanly, a lock file willexist. Select Unlock in the dialog box that appears.

2. The next dialog box that appears asks if you want to recover the last saved state before opening. SelectNo here despite the warnings.

Your Project Schematic now shows a state as if the solution had not started, but examination ofthe project files shows that backup files are available. Your Workbench project will not know aboutthese files.

3. Populate the restart data from the participant systems connected to System Coupling. Make sure thatthese restart points correspond to the restart point chosen in System Coupling.


4. Recover the System Coupling restart points:

a. On the Project Schematic, right-click System Coupling's Setup cell, and select Update.

b. Double-click the System Coupling Setup cell to open the System Coupling tab.




c. Select Analysis Settings, then in Properties of Analysis Settings, right-click Coupling Initializationand select Read Restart Points.

The restart points will now be available in System Coupling as usual.

d. In Properties of Analysis Settings > Coupling Initialization, pick a restart point that correspondsto the restart point you selected in the participant systems.

5. You can now start your restart run. To do this, in the System Coupling tab, right-click Solution and selectUpdate. Your restarted coupled analysis will now begin to solve.

Stopping the Coupled Analysis Run

During the analysis run, you may wish to interrupt or abort the analysis before it is completed. The in-terrupted analysis can be thought of as a clean stop, where the run continues until the current couplingstep is finished, and the restart data are generated. Such a run can be restarted later from end of thecoupling step in which it was stopped, as described in Restarting a System Coupling Analysis (p. 35).The aborted analysis, on the other hand, terminates the run immediately. This run cannot be restartedfrom the coupling step in which it was stopped.

The workflow for stopping the coupled analysis run in Workbench is as follows:

1. Start the analysis by selecting Update from the context menu of the Solution cell of the System Couplingcomponent.

2. In the Progress view of Workbench, click the Stop button .

3. A popup window, shown in Figure 5: Interrupt Prompt from Workbench (p. 38), will appear asking howthe run should be stopped.

Figure 5: Interrupt Prompt from Workbench

You can choose from the following options:

• Select Interrupt to perform a clean shutdown. The analysis will stop once the current couplingstep is completed.

• Select Abort to stop the analysis run immediately. All available generated data will be discarded.

• Select Cancel to continue with the current run.

4. See Restarting a System Coupling Analysis (p. 35) for information on how to restart the coupled analysisrun.



If you are running your analysis from the command line, to stop a run an scStop.stop file must becreated in the working directory for the System Coupling service. See System Coupling Service ShutdownFile (scStop.stop) (p. 55) for more information.



Stopping the Coupled Analysis Run


Understanding the System Coupling Service

This chapter provides information about the System Coupling Service used in the execution of coupledanalyses. The two main roles of the coupling service are: coupling management, and the mapping ofdata transfers. This chapter also describes the various files used by and generated by the coupling service.

Coupling ManagementData TransfersFiles Used by the Coupling ServiceFiles Generated by Coupling ServiceUnderstanding the System Coupling Input FileUnderstanding the System Coupling Log File

Coupling Management

The primary role of the System Coupling Service is to manage the coupled analysis. There are threeaspects to this:

• Inter-Process Communication

• Process Synchronization and Analysis Evolution

• Convergence Management

For more information, see the following sections.Inter-Process CommunicationProcess Synchronization and Analysis EvolutionConvergence ManagementEvaluating Convergence of Data Transfers

Inter-Process Communication

The coupling service and participants, which are often highly optimized physics solvers, are executedas independent computational processes, and this introduces the need for Inter-Process Communication(IPC). This communication is realized using a proprietary, light-weight, TCP/IP based client-server infra-structure that does not interact with other communication mechanisms like the Message Passing Interface(MPI).

All high level communication needed for process synchronization, brokering data transfers and managingconvergence between the coupling service and participants are defined in terms of Application Pro-gramming Interfaces (APIs) that use the low level IPC infrastructure.

Process Synchronization and Analysis Evolution

The coupling service and participants advance synchronously through a coupled analysis. High-levelsynchronization is managed with the use of synchronization points, and low-level synchronization,between synchronization points, is managed using a token-based protocol.



The five primary synchronization points used to manage advancement through the coupled analysisare shown in Figure 6: Execution Sequence Diagram for the Coupling Service and Co-Simulation Parti-cipants (p. 42). This figure also features notes regarding the processing that occurs between thesepoints, as well as the coupling step and iteration loop structure. Each of these synchronization points,shown in dark gray, represents a gateway beyond which a given process may not advance until allother processes (or a subset thereof, as controlled by the coupling service) arrive. Note, as well, thatwhile a process may serve data both between and at synchronization points, it may only request databetween synchronization points.

Figure 6: Execution Sequence Diagram for the Coupling Service and Co-Simulation Participants

Details regarding processing between the Solution and Check Convergence synchronization pointsare shown in Figure 7: Processing Details for the Coupling Service and Co-Simulation Participants (p. 43).During this stage of the analysis, the coupling service controls the advancement of co-simulation parti-cipants, or solvers, through two secondary synchronization points: Data Transfer and Solve, bothshown in light gray. The sequencing of solvers is controlled by manipulating the relative order in whichthe solvers advance beyond these secondary synchronization points. For example, solvers withidentical sequence indices all advance through the Data Transfer synchronization point together, andthen do the same for the Solve synchronization point.



Figure 7: Processing Details for the Coupling Service and Co-Simulation Participants

These figures highlight that all participants traverse the duration of the entire coupling step duringeach coupling iteration. They have complete freedom, however, to traverse the coupling step durationin one or more ‘solver’ steps, each of which may include one or more solver iterations. If multiple‘solver’ steps are used within one coupling step, then this is referred to as sub-stepping (or sub-cycling).Review the participant systems’ documentation to see if sub-stepping occurs and is supported withSystem Coupling.

Convergence Management

By default, the system coupling log file reports Root Mean Square (RMS) convergence for data transfersfor both the source and target side of the transfer. Convergence of the coupling step is evaluated atthe end of each coupling iteration. Coupling step convergence requires that:

• the target side RMS values have reached the convergence criteria that you specified in the input to thesystem coupling setup, and

• that the minimum number of coupling iterations that you specified are met.

If the coupling step is not yet converged, then a new coupling iteration is started. If the coupling stepis converged, then a new coupling step is started if the coupling duration has not yet been reached.

Evaluating Convergence of Data Transfers

To evaluate convergence of data transfers, each iteration is measured against the previous iteration.The change in all of the data transfer values between these two successive iterations is reduced to anormalized value. When two successive iterations produce a normalized value that is under the conver-gence target (you can change this convergence target, the default value is 1e-2), the data transferredis converged.



Coupling Management

Two global (that is, over all locations) measures of convergence are evaluated and reported during ex-ecution of the coupled analysis. These include the maximum and Root Mean Square (RMS) of the nor-malized change in data transfer values. The RMS is the default measure used to determine convergence.The measure can be changed to the maximum of the normalized value through the System CouplingInput file.

The RMS value is evaluated as:

(1)

where is the normalized change in the data transfer value between successive iterations within/acrossa given coupling step, and is measured as:

(2)

where is the data transfer value, and l is the location of the data transfer on the coupling interface.

In Equation 2 (p. 44), the denominator, or normalization factor, is evaluated differently in the transientand general coupling analyses. In the transient coupling case, the normalization factor equals the averageof the range and mean of the magnitude of data transfer values over all locations for the current iteration.In the general coupling case, it equals the average of the range and mean of the magnitude of datatransfer values over all locations for all iterations in the entire analysis. This normalization factor is arepresentative scale for the data transfer values and ensures that division by zero (due either to zerorange or zero mean) is avoided.

In Equation 2 (p. 44), the numerator, , is the un-normalized change between successive iterations,and is expressed as:

(3)

where and correspond to the current and the previous iterations respectively, and is the

under-relaxation factor applied in forming the final value applied during the current iteration. In thefirst coupling iteration of every coupling step, is assumed to be unity.

When there is no change in data transfer values, the default for RMS/MAX is 1.0e-014.

Note

The global data transfer convergence measures are set to unity in the first coupling it-eration of the first coupling step during an initial run. After a restart, if a data transferinvolving a new variable is defined or if the region is remeshed, these measures are setto unity in the first coupling iteration of the first coupling step.

Although monotonic convergence to the specified target values is ideal, oscillatoryconvergence and/or divergence (that is, constant or increasing convergence measures)may also occur.

Data Transfers

Data transfers in System Coupling use one of two data transfer algorithms:



• Profile Preserving data transfer algorithm is used when transferring non-conserved quantities like dis-placements and temperatures.

• Conservative Profile Preserving data transfer is used when transferring conserved quantities like mass,momentum, and energy flows (for example, forces).

These two data transfer algorithms are discussed in the section Data Transfer Algorithms (p. 46). Bothdata transfer algorithms incorporate the following components:

• Data Pre-Processing: This is the first component used in the data transfer process and could involvecreation of supplemental data on mesh locations that are needed by the mapping and interpolationalgorithms.

• Mapping: This is the second component used in the data transfer process and involves the match-ing/pairing of a source and a target location to generate weights. For example, in a fluid-solid interactionproblem, a fluid node must be mapped to a solid element to receive displacements. Similarly, either asolid node or a Gauss point in a solid element must be mapped to a fluid element to receive stress.

• Interpolation: This is the third component used in the data transfer process and involves the (re)useof the generated weights to project source data onto target locations.

• Interpolated Data Post-Processing: This is the final component of the data transfer process and couldinvolve explicit under-relaxation, ramping, and/or clipping of the target data, as well as the creation ofsupplemental data on mesh locations needed by the consumers of interpolated, target data.

Note that participant data transfer regions must consist of triangular or quadrilateral faces. Polyhedralfaces as well as faces with hanging nodes (cut-cells) are not supported by System Coupling.

A variety of algorithms exist in the literature to address these components. In the discussions below,only those that are used in System Coupling are presented.

• Data Pre-Processing Algorithms (p. 45)

• Mapping Algorithms (p. 46)

• Interpolation Algorithms (p. 52)

• Interpolated Data Post-Processing Algorithms (p. 53)

Important

Unit conversions are automatically applied for all data transfer algorithms during each of themapping and interpolation phases.

Data Pre-Processing Algorithms

Data pre-processing algorithms are used to create supplemental data on mesh locations that are neededfor mapping and interpolation. These pre-processing algorithms may also be used during post-processingof interpolated data to provide data on the mesh locations required by co-simulation participants.

Creating Nodal Data from Face/Element Centroid Data

Conservative data (for example, heat flows and forces) may be available on element (face) centroids. Ifthese data are required on nodes, the following steps are executed:



Data Transfers

• an element-node value is calculated by dividing the total value by the number of nodes that define theelement, and

• the element-node values are scattered to, and accumulated at, each node.

Creating Face/Element Data from Node Data

Conservative data (for example, heat flows and forces) may be available on nodes. If these data are re-quired on elements/faces, the following steps are executed:

• the area for each face/element that shares a common node is calculated for all nodes,

• the nodal area is calculated as the sum of all areas for each face/element that shares a common node,

• the area fraction is calculated as the area divided by nodal area for each face/element that shares a commonnode, and

• the face/element value is calculated for each element-node as the nodal value times the respective areafraction.

The face/element values corresponding to each element-node are summed if a total face/element valueis required.

Mapping Algorithms

Several mapping algorithms are used when executing data transfers during system couplings. To assistin evaluating the quality of the mapping, a mapping summary is included in the System Coupling servicelog file (see System Coupling Service Log File (scLog.scl_, scLog_##.scl) (p. 57)). Note thatsummary data depends upon on the availability and relevance of specific information (for example, thenumber of nodes or area on the surface and/or target meshes) for each mapping algorithm.

Mapping is performed only at the start of the System Coupling simulation. Because of this, the meshtopology on the data transfer regions cannot change (that is, cannot be dynamically remeshed) duringthe simulation.

The two mapping algorithms used in System Coupling (discussed below) are Bucket Surface and Gen-eral Grid Interface (GGI).

Data Transfer Algorithms

Data transfer algorithms are combinations of mapping/interpolation algorithms (discussed in the sectionsabove) that are used in the System Coupling service.

Note that the fidelity of the data transferred to the target side of the interface is limited by the least-resolved side of the interface. For example, if the target side of the interface is significantly coarser thanthe source side, then only the large scale features of the source data will be captured in the data



transfer. Similarly, if the target side of the interface is significantly finer than the source side, then theresulting target data will be a linearly interpolated representation of the data on the source side.

Note

A number of advanced controls for the data transfer algorithms are exposed via expertsettings. For more information, see Expert Settings Related to Mapping in ExpertSettings (p. 24).

Profile Preserving

The Profile Preserving data transfer algorithm is the default algorithm used by System Coupling whentransferring non-conserved quantities like displacements and temperatures. For this data transfer al-gorithm, the Bucket Surface mapping algorithm is used to generate mapping weights. In this algorithm,the mesh nodes on the target side of the data transfer interface are mapped onto mesh elements onthe source side as illustrated in Figure 8: Mapping target node to source element for Profile PreservingData Transfer (p. 47). Standard, weight-based interpolation (resulting in the values shown) and sub-sequent under-relaxation are used to evaluate the final data applied on the target side of the interface.

Figure 8: Mapping target node to source element for Profile Preserving Data Transfer

Profile Preserving data transfer algorithm is the default algorithm used when transferring non-conser-vative quantities because of the profile-preserving nature of the mapping weights generated by theBucket Surface algorithm.

Conservative Profile Preserving

The Conservative Profile Preserving data transfer algorithm is the default algorithm used by SystemCoupling when transferring conserved quantities like mass, momentum, and energy flows (for example,forces). For this data transfer algorithm, the General Grid Interface (GGI) mapping algorithm is used togenerate mapping weights. Standard, weight-based interpolation and subsequent under-relaxation areused to evaluate the final data applied on the target side of the interface.

Conservative Profile Preserving data transfer algorithm is the default algorithm used when transferringconserved quantities because of the conservative nature of the mapping weights generated by the GGIalgorithm. Resulting target values are locally (in the vicinity of each source and target element) conser-vative. If the source side of the interface is completely mapped to the target side of the interface, thenthe resulting target values are also globally conservative. If any portions of the source side of the interfaceare not mapped onto the target side, then the data transfer is not globally conservative. Note that anyportions of the target side of the interface that are unmapped (that is, weights equal to zero) areautomatically assigned a value of zero, which differs from the handling of unmapped nodes using theProfile Preserving data transfer algorithm.



Data Transfers

Bucket Surface

The underlying ideas for this algorithm are presented in the book Computational Nonlinear Mechanicsin Aerospace Engineering, American Institute of Aeronautics and Astronautics, edited by S. Atluri, ISBN1563470446, Chapter 5, Fast Projection Algorithm for Unstructured Meshes by K. Jansen, F. Shakib, and T.Hughes, 1992. Specifically, the implementation of the Smart Bucket Algorithm as described in the chapterstated above is used in system coupling. This algorithm generates weights that are ideal for transferringthe profiles of non-conserved quantities like stresses, displacement, temperature, and heat transfercoefficient from a source mesh to a target mesh. Since a complete description of the algorithm isavailable in the reference quoted above, only a brief overview of it is presented below.

The first step in the process of computing the mapping weights using the Smart Bucket Algorithm isto divide the mapping source mesh into an imaginary structured grid, with each grid section called a“bucket.” A 2D bucket is used to demonstrate this concept in Figure 9: Example of a Bucket Grid on a2D Source Mesh (p. 48). Similarly, a 3D bucket grid is generated for a 3D mesh, and this is what is usedin System Coupling.

Next, each node on the data transfer regions of the target mesh is initially associated with a bucket. InSystem Coupling, data transfer regions consist of element faces from the 3D mesh. Two cases arise:buckets associated with the target node are either empty (without even one source element in it) ornon-empty. For example, bucket A shown in Figure 9: Example of a Bucket Grid on a 2D SourceMesh (p. 48) is empty. Each case (empty and non-empty buckets) is discussed separately in the sectionsbelow.

Figure 9: Example of a Bucket Grid on a 2D Source Mesh

Case 1: The bucket associated with a target node is non-empty

If the bucket associated to a given target node is non-empty, the mapping algorithm attempts to matcheach of the target nodes to one source element in the bucket.



First, each target node is checked to see if it is in the domain of any of the source elements. This isdone by looping through all the source elements in that bucket and checking to see if the target nodeis within their domain. For each source element in the bucket, the vector element–local (or natural)

coordinates (corresponding to the vector of global coordinates of the target node, ) is found bysolving the set of nonlinear equations given by the isoparametric mapping below:

(4)

where is the matrix of linear shape functions associated with the source element and is

the vector of global coordinates of element–local node . It is then checked to see if lies within thedomain of the source element based on certain criteria discussed next.

For a four-noded quadrilateral source element, if the natural coordinates corresponding to a targetnode satisfy the conditions in Equation 5 (p. 49) below, the target node is said to be exactly within thedomain of the element.

(5)

where and are the components of the vector of natural coordinates . However, if the naturalcoordinates do not satisfy the conditions in Equation 5 (p. 49) but do satisfy the ones in Equation 6 (p. 49)below, then the target node is in the domain of the source element but only within the specified toler-ance (also known as element edge tolerance). The value of tolerance is exposed in the SystemCoupling UI as one of the expert settings. See the description of ProfMapEdgeTol in the sectionExpert Settings Related to Mapping in Expert Settings (p. 24).

(6)

This concept is explained with the help of Figure 10: A Quadrilateral Source Element in the Natural Co-ordinate Space (p. 50) wherein a quadrilateral source element is shown along with two different targetnodes, one of which satisfies Equation 5 (p. 49), and other that satisfies Equation 6 (p. 49).



Data Transfers

Figure 10: A Quadrilateral Source Element in the Natural Coordinate Space

Similarly, for a three-noded triangle element, the conditions listed in Equation 7 (p. 50) below, are usedto check if a target node is exactly within the domain of the element:

(7)

And the conditions in Equation 8 (p. 50) below will determine if the target node is within the domainbut up to a tolerance .

(8)

Now that target nodes are determined to be in the domain of specific source elements, each node mustbe paired with only one source element. In both of the cases above (four-noded quadrilateral and three-noded triangle), it is possible that a target node occurs (either exactly or within a tolerance) in morethan one source element’s domain. The finite element interpolation of the nodal solution requires eachtarget node to be paired with only one source element.

To satisfy this requirement, the target node is consequently paired with that source element for whichthe gap is minimized. The gap is defined as the Euclidean distance between the target node and itsprojection onto/into a source element. In some cases, such as when candidate source elements are co-planar, the gap values may be identical and an alternate approach is required to pair the target nodewith one source element. Under these conditions, only the source elements with identical (and minimized)gaps are considered. The target node may be exactly in the domain of any of these source element, or



it will be in their domain within a tolerance. Preference is given to the last source element for whichthe target node is exactly in its domain. If the target node is only in the different domains within atolerance, then the last candidate source element is used.

Once the target node is paired with a source element, mapping weights are computed by evaluatingthe finite element shape functions associated with the paired source element at the target node.

If no target node-to-source element match is found in a non-empty bucket, then the target node is re-ported as being unmapped. It is important to note, however, that mapping weights are still evaluatedfor such nodes using the Bucket Surface Algorithm. Specifically, all unmapped target nodes are simplymapped to the nearest source node in the bucket and the target node is assigned the solution valuecorresponding to that source node.

Note

Significant ‘gap’ distances between successfully-mapped target nodes and source elementsmay occur. For information about how to have mapped nodes with ‘gap’ distances largerthan a specified tolerance be reported as unmapped, see Expert Settings Related to Mappingin Expert Settings (p. 24).

Case 2: The bucket associated with a target node is empty

If the bucket initially found for the target node is empty, then the closest non-empty bucket is foundand the same procedure as highlighted in Case 1 is followed so that each target node is mapped toone source element and mapping weights are calculated.

Unmapped Nodes

With the Bucket Surface algorithm, there are two types of target nodes that can be reported as un-mapped: nodes that do not fall within a bucket (these are “unmatched nodes”), and nodes that do fallwithin a bucket, but that do not meet the gap tolerance (these are "gap nodes”). Unmatched nodesare mapped to the nearest source node in the bucket and the target node is simply assigned the solutionvalue corresponding to that source node. Unmatched nodes are always reported as unmapped in theSCL file. Gap nodes are within a bucket, and so are mapped to the source nodes like all of the othermapped nodes and given a value accordingly. Gap nodes are reported as mapped in the SCI file. Thegap tolerance and the reporting of gap nodes in the SCI file can be modified using Expert Settings (p. 24).

General Grid Interface (GGI)

The underlying ideas for this algorithm are presented in the article on Three- Dimensional Navier StokesPredictions of Steady-State Rotor/Stator Interaction with Pitch Change, 3rd Annual Conference of the CFD,Society of Canada, Banff, Alberta, Canada, Advanced Scientific Computing Ltd, by P.F. Galpin, R.B. Brobergand B.R. Hutchinson, June 25-27, 1995. This algorithm generates weights that are ideal for transferringconserved quantities such as mass, momentum and energy flows.

In this algorithm, each element face on both the source and the target sides is first divided into n integ-ration point (IP) (sub-) faces, where n is the number of nodes on the face. The three-dimensional IPfaces are then converted into a two-dimensional quadrilaterals made up of rows and columns of pixels.Pixels from the converted quadrilaterals on the source and target sides are intersected, creating anumber of overlapped areas called ‘control surfaces.’ Mapping weight contributions are evaluated foreach control surface based upon the associated source and target element face areas and the pixel in-tersections. Final mapping weights for each of the target (or source) nodes are evaluated by accumulatingthese control surface contributions.



Data Transfers

If no control surfaces are created (for example, when no polygon intersection between mapping sourceand target exists), then mapping weights are identically zero and nodes and elements on the target (orsource) side of the interface are reported as being unmapped.

As an example, consider the schematic shown in Figure 11: General Grid Interface Mapping (p. 52) thatcorresponds to a typical interface between the source (sending) and target (receiving) sides. In theschematic, the control surfaces resulting from the intersection of all IP faces on the interface (labeledwith an ‘X’), are shown. For example, the IP faces S1 and S2 on the source side intersect with the IPfaces R1 and R2 on the target side creating areas A1, A2, and A3 on the control surface. In this case,the mapping weight contributions for the target IP face R1 (and associated target node) that are asso-ciated with the source IP faces S1 and S2 (and nodes) are respectively given by:

(9)

and

(10)

Figure 11: General Grid Interface Mapping

Interpolation Algorithms

The interpolation algorithm is responsible for providing target node values using the source data andmapping weights that were generated by the mapping algorithm(s) (see Mapping Algorithms (p. 46)).The mapping weights are applied in Equation 11 (p. 53) to evaluate , which is the target node, or it-eration point (IP) face value.



(11)

where is the value at the source node, and is the associated weight. For weights obtained

with the bucket surface mapping algorithm, is the number of nodes in the source element. For weightsobtained via the GGI mapping algorithm, is the number of areas (associated with a target IP face)obtained due to the intersection of the sender and receiver faces on the control surface.

Interpolated Data Post-Processing Algorithms

Interpolated data post-processing algorithms are the last step in the data transfer process. In manysituations (such as an implicit coupling where the number of coupling iterations within a coupling stepis more than one), the interpolated target data needs to be post-processed before it is exposed to thetarget participant of the data transfer. Two optional post-processing algorithms may be applied to thetarget data generated during interpolation: ramping and under-relaxation. Each of these algorithms isused to improve convergence of the overall analysis. Other post-processing algorithms that are auto-matically applied involve:

• clipping unphysical data values (p. 55), and

• creation of supplemental data on mesh. For information on the creation of supplemental data, see DataPre-Processing Algorithms (p. 45).

Unless otherwise noted, post-processing algorithms are applied to each:

• data transfer location (node), and

• component of vector data transfers

Ramping Algorithm

The ramping controlled by the System Coupling service works by slowing the application of the source-side value on the target-side of the data transfer. For each data transfer location (node) where is true, the following formula is applied:

(12)

where

is the ramped, target-side value.

is the reference target-side value, which for the first coupling step is the initial

value for the data transfer variable (see Table 3: Initial Values used for the ReferenceTarget-Side Value (p. 54)). Thereafter, the reference target-side value is the final valuefrom the previous coupling step. The one exception is displacement, where for everycoupling step, is always 0.0 [m].

is the raw, target-side value obtained from interpolation.

is the current coupling iteration number within the coupling step.

is the minimum number of coupling iterations per coupling step.



Data Transfers

Under-Relaxation Algorithm

Under-relaxation works by limiting a potentially large variation of the target-side data between twosuccessive coupling iterations. For each data transfer location (node), the following formula is applied:

(13)

where

is the relaxed, target-side value.

is the reference target-side value. For coupling iterations within a coupling

step, the reference target-side value is the final value from the last coupling iteration.For the first coupling iteration of the first coupling step, the reference target-side valueis the initial value for the data transfer variable (see Table 3: Initial Values used for theReference Target-Side Value (p. 54)). For the first coupling iteration of all subsequentsteps, the reference target-side value is the final value from the last coupling step.

is the raw, target-side value obtained from interpolation or from ramping (if applied).

Note that if you have applied both ramping and under-relaxation, the data is first rampedand then under-relaxed. In this case, for the under-relaxation’s raw

target-side value.

ω is the under-relaxation factor (URF). In a transient analysis, in the first coupling iterationof every coupling step, the URF is overridden and set to 1, and so data transferred atthis coupling iteration is not under-relaxed.

Initial Values used in Ramping and Under-Relaxation Algorithms

The default for the initial value used as the reference target-side value ( ) in Equation 12 (p. 53)

and Equation 13 (p. 54) is based on the physical type of the variable. The default values are listed inTable 3: Initial Values used for the Reference Target-Side Value (p. 54).

Table 3: Initial Values used for the Reference Target-Side Value

NotesInitial Value used for theReference Target-SideValue ( )

VariableType

For the ramping algorithm,the reference target-side

0.0 [m]Incrementaldisplacement

value for incrementaldisplacement is always 0.0[m] for every coupling step.

0.0 [N]Force

Variables of this type includetemperature and near walltemperature.

295.15 [K]Temperature

0.0 [W]Heat Rate

0.0 [Wm-2K-1]Heat TransferCoefficient



These defaults for the initial values above can be overridden using the methods discussed in the sectionExpert Settings (p. 24). Note that for the ramping algorithm, the reference target-side value for displace-ment cannot be modified using expert settings.

Clipping Algorithm

Although uncommon, it is possible that unphysical values, such as negative heat transfer coefficients,are provided by the data transfer source or are generated during mapping. To ensure unphysical valuesare not applied to the data transfer target, these unphysical values are clipped to be within a valid

range. For example, any negative heat transfer coefficient values are changed to 0 [Wm-2K-1] beforebeing transferred to the target participant.

The variable(s) that are clipped and their valid range are listed in the table below. Note that at the endof any coupling step where clipping is used, the System Coupling Log file will have a message aboutthe clipping.

Maximum ValueMinimum ValueVariableType

unlimited0 [Wm-2K-1]Heat TransferCoefficient

Files Used by the Coupling Service

This section outlines the files used by the coupling service during its execution.System Coupling Service Input File (scInput.sci)System Coupling Service Shutdown File (scStop.stop)

System Coupling Service Input File (scInput.sci)

The scInput.sci file, which is an XML file generated by the System Coupling system in Workbench,provides analysis-related inputs to the coupling service. The input XML file is composed of several dif-ferent sections: participants, analysis, transfers, and execution control. You can modify this file, with anappropriate XML editor, although this is not encouraged.

When the System Coupling system's Setup cell is up-to-date and the System Coupling user interface isactive (by editing either the System Coupling Setup or Solution cell), you will be able to export, andsave, the input file using the Export SCI File option available from the Workbench File menu.

For more detailed information about the input file contents, see Understanding the System CouplingInput File (p. 58).

System Coupling Service Shutdown File (scStop.stop)

If a text file named scStop.stop is found in the coupling service’s run directory, then the service willshut down as soon as possible. The shutdown file should contain two (or more) lines as shown below:

0The reason for terminating the analysis

The first line contains an integer flag that indicates whether or not the termination should be interpretedas an ‘interrupt’ or as a ‘stop’.



Files Used by the Coupling Service

• With an integer value of 0, the analysis will be interrupted; the coupling service will complete the currentcoupling step and signal the co-simulation participants that the execution has ended. This will cause thecoupling service and participants to shutdown cleanly.

• With an integer value of 1, the analysis will be stopped; the coupling service will signal the co-simulationparticipants to abort the run as quickly as possible. This will not produce a clean shutdown.

The second and subsequent lines in the file are reported in the coupling service’s log file when summar-izing the reason for shutting down the coupled analysis.

Files Generated by Coupling Service

This section outlines the files generated by the coupling service during its execution.System Coupling Server File (scServer.scs)System Coupling Service Log File (scLog.scl_, scLog_##.scl)System Coupling Results File (scResults_##_######.scr)

System Coupling Server File (scServer.scs)

The scServer.scs file, which is written to the service’s run directory, contains information that isused to connect the participants to the coupling service. This file is generated shortly after the couplingservice is started, and indicates that the coupling service is ready to receive connections from the co-simulation coupling participants.

This text file contains the following lines of data:

• The server’s port and host, separated by an ‘@’ character.

• A block containing the number of co-simulation participants connected to the System Coupling systemin the Workbench schematic, and their unique and display names. In the Workbench environment:

– the unique names are automatically generated and are reported as the ComponentID in the Prop-erties view of the co-simulation participant’s Solution cell,

– the display names correspond to the names (which you are able to specify) below the participant’ssystem

Example 1: An Example scServer.scs File

[email protected]

2

Solution 1

Fluid Model

Solution 2

Solid Model

Note

When the participants are started and instructed to connect to the running SC Service, theymust connect to the service using the unique names (for example Solution 1 andSolution 2 in the example above).



System Coupling Service Log File (scLog.scl_, scLog_##.scl)

The scLog.scl file provides key runtime information related to a coupled analysis between variousparticipants, including:

• The command line used to start the system coupling service

• System coupling header and build information

• A summary of system coupling setup information, including:

– Analysis information

– Coupling participant information (number of participants, and summary information pertaining toeach participant)

– Data transfer information (number of data transfers, and summary information pertaining to eachdata transfer)

– Execution control information (co-simulation sequence, debug output)

– Setup validation (summary of system coupling input file validation)

– System coupling co-simulation summary (summary of system coupling participants)

• Solution information, including:

– Mapping summary (including percentages of mapped source and target nodes and the percentagesof mapped source and target areas, depending upon the mapping algorithm that was used)

– Convergence information at each coupling step and iteration

The information here includes the coupling step index, the current analysis time for transientcouplings, the coupling iteration index, the participant name and data transfer name, theparticipant convergence status (for example, “Not Yet Converged...”, “Converged”, and so on),and the data transfer convergence (for example, the RMS/Maximum normalized change).

• Shutdown information, including:

– Run completion status

During the execution of a run, the service log file, named scLog.scl_, is generated, evolving withthe analysis, and is finally renamed at the end of the run. The final log file is named with the convention:scLog_##.scl, where the suffix _## denotes the run index. For example, scLog_13.scl correspondsto the 13th run (that is, the 12th restart) executed for the analysis.

For more detailed information about the log file contents, see Understanding the System Coupling LogFile (p. 64).

System Coupling Results File (scResults_##_######.scr)

The system coupling results file contains important data generated and used by the system couplingservice during the analysis. This data enable you to:

• Restart the analysis or continue from a previous analysis



Files Generated by Coupling Service

• Post-process the heavy weight interface data

• Monitor the analysis’ convergence

• Reconstruct the analysis

The specific data contained in the file are summarized as:

• A history of the input (SCI) files used to drive the coupling service’s execution

• Convergence data corresponding to the data transfers and solvers’ field equations

• Heavyweight data corresponding to the source and target regions and variables for defined data transfers

A system coupling results file is always created at the end of the analysis. The default file naming con-vention is of the form scResults_##_######.scr, where the run index is recorded in the “_##”suffix and the coupling step index is recorded in the “_######” suffix (for example, scRes-

ult_13_000101.scr corresponds to the 101st coupling step within the 13th run of the analysis). In-termediate results files, with the same naming convention, can also be created at various coupling stepintervals (defined by you) during the analysis.

Important

All data stored in the System Coupling Result file(s) are written in the SI unit system.

Understanding the System Coupling Input File

The input XML file is composed of several different sections: participants, analysis, transfers, and executioncontrol.

The participant section contains information obtained through the coupling data interface (CDI) andthe connections to upstream solver systems. It is intended to be read-only. In the participants section,you can view the Count (an integer representing the number of connected participants). For eachconnected participant, you can view the following: Note that depending upon the type of participant(co-simulation or static data), some of the options may or may not be applicable.

• Type (integer attribute)

The type of coupling participant (0 – co-simulation, 1 – static data)

• Name (string)

The name of the participant. This is the name with which the participant identifies itself to the systemcoupling. This corresponds to the “Component ID” which is unique to a specific system’s Solutioncell in the Workbench user interface.

• DisplayName (wide string)

The display name of the participant provided by you in the in Workbench user interface.

• FilePath (string)

The full path to the primary file used to access source data from a static data participant.



• SupportsCouplingIterations (boolean)

Whether or not the co-simulation participant supports the execution of multiple coupling iterationsper coupling step.

• UnitSystem

• Regions (options below are applicable to an individual region)

– Name (string)

The name of the region (intrinsic to the participant).

– DisplayName (wide string)

The display name of the region given by you in the Workbench user interface.

– TopologicalDimensionality (integer)

The geometry type of the region (0 – undefined, 1 – point, 2 – curve, 3 – surface, 4 – volume).

• Variables (options below are applicable to an individual variable)

– Name (string)

The name of the variable (intrinsic to the participant).

– DisplayName (wide string)

The display name of the variable given by you in the Workbench user interface.

– PhysicalType (string)

The physical type of the variable (options include: Length / Force).

• BaseUnits (strings denoting base units for all data of noted physical type)

– Length (string)

– Time (string)

– Mass (string)

– Luminance (string)

– Angle (string)

– SolidAngle (string)

– Temperature (string)

– ChemicalAmount (string)

– Current (string)

The analysis section contains details used to define the coupled analysis. In the analysis section, youcan set the following:




• AnalysisType (integer)

This setting defines the nature of the sequential steps used in coupling co-simulation participants.Available option is 0 (general), and 1 (transient).

• Initialization

This setting defines the initial time for the coupled analysis

– Option (integer)

Available options are 0 (Program Controlled) and 1 (Start Time). The former is the default optionfor coupling initialization. When this option is used, the coupling service will make the most appro-priate choice of an initial time value. When the latter option is used, the coupling service willoverride the initial/start time for the analysis with the value specified as part of Time (see below).

– Time (double)

If option 1 is chosen above, then this is the initial time for the coupling analysis.

• Duration

This setting defines the duration of the coupled analysis.


Available options are 0 (NumberOfSteps) and 1 (EndTime).

– NumberOfSteps (integer)

This option is available only if no end-time requirements exist for co-simulation participants.

– Time (double)

Final time of coupling analysis.

• Step

– MaximumIterations (integer)

The maximum number of coupling iterations allowed per coupling step.

– MinimumIterations (integer)

The minimum number of coupling iterations allowed per coupling step.

– Size (double)

The size of the coupling step when it is associated with a time (this is done for transient analyses,size is measured in seconds).


Available option is 1 (coupling step size, used for transient analyses) and 0 (non dimensional stepsize, used for general analyses).



• UnitSystem (string)

The transfers section contains details used to define the data transfers between any static and co-sim-ulation coupling participants. In the transfers section, you can set the Count (an integer representingthe total number of data transfers) as an attribute. For each coupling transfer, you can set the following:

• Name (string)

The name of the transfer (which you provided) in the Workbench user interface.

• ExecuteCouplingAt (integer)

This setting defines “when” the current data transfer is executed during the coupled analysis. Theonly available option is 2 (Start of Iteration).

• Source

The information related to the source participant involved in the data transfer.

– Participant (string)

The name of the source participant.

– Region (string)

The name of the source region (defined for a given participant) participating in the data transfer.

– Variable (string)

The name of the source variable, the data corresponding to which is exchanged during the datatransfer (also defined for a given participant).

• Target

The information related to the target participant involved in the data transfer

– Participant (string)

The name of the target participant

– Region (string)

The name of the target region participating in the data transfer

– Variable (string)

The name of the target variable, the data corresponding to which is exchanged during the datatransfer

• ConvergenceOption (integer)

Specifies the type of data transfer convergence check in an implicit coupling (that is, if more thanone coupling iteration per coupling step is specified; a value of 0 indicates the RMS normalizedchange).

• ConvergenceTarget (double)




The target value that determines the convergence of the data transfer

• UnderRelaxationFactor (double)

The under-relaxation factor (URF) applied to the data increments between any two successive couplingiterations. The URF has a range of . Note that when transferring incremental displacement,the URF must equal 1. In this case, a value less than 1 can lead to an accumulation of errors, and thefollowing warning will be displayed in your SCL file:

The under relaxation factor for the data transfer named '<name of data transfer>' is smallerthan one. Under relaxation factor less than one for incremental displacement might lead to errors.

• Ramping (integer)

This setting defines if and how ramping is used when applying data from the source-side to the target-side of the data transfer. Valid options are: 0 – none (that is, stepped), and 1 – linearly ramped up tothe minimum number of coupling iterations. The default is none, which implies the target side ofthe data transfer experiences the full value from the source side during the first coupling iteration.

The execution control section contains details used to define the solution sequence between thecoupling participants, the system coupling debug output, intermediate result files output, and expertsettings. For each participant, you can set the following:

• CoSimulationSequence

This subsection is used to specify the sequencing of co-simulation coupling participants (most oftensolvers) during a coupling iteration. In the CoSimulationSequence subsection, the 'Count' attributespecifies the number of participants for which sequencing information will be provided.

– Participant

A Participant subsection is required for each co-simulation participant.

→Name (string)

The name of the participant.

→SolutionSequence (integer)

The sequence number of the participant in the coupled solution. Within a coupling iteration, aparticipant with a larger sequence number will solve later than another with a lower sequencenumber.

• DebugOutput

This subsection is used to specify the section(s) of debug output to write to the system coupling log(SCL) file. As presented below, the level of detail is specified for each section or all sections (the default).

– DefaultOutputLevel (integer)

This setting provides the default level for the different sections of debug output. If this entry is setand another specific entry (for example, Startup) also exists, then the output level for the specificentry will override the level set here.

– Startup (integer)



This setting controls the level of output from the start of the coupling service until creation of the“Summary of SC Setup” banner in the SCL file.

– ParticipantConnection (integer)

This setting controls the level of output from the end of the setup validation until the “Initial Syn-chronization” synchronization point.

– AnalysisInitialization (integer)

This setting controls the level of output from the “Analysis Initialization” until the “Solution” syn-chronization point.

– SolutionInitialization (integer)

This setting controls the level of output during the setup of coupling steps and iterations. Thisoutput does not include information related to the data transfers.

– ConvergenceChecks (integer)

This setting controls the level of output from the “Check Convergence” synchronization point untilthe next synchronization point, which may be either “Shutdown” or “Solution.”

– Shutdown (integer)

This setting controls the level of output after the “Shutdown” synchronization point.

– Transfers

This section is used to specify the debug output generated for data transfers. Note that headerinformation for mapping is generated whenever the mesh coordinate or mesh topology output isrequested. Similarly, header information for the data transfers is generated whenever the transferdata output is requested.

→DefaultOutputLevel (integer)

This setting provides the default level for the different kinds of debug output. If this entry is setand another specific entry (for example, SourceMeshCoords) also exists, then the output levelfor the specific entry will override the level set here.

→SourceMeshCoords (integer)

This setting controls the level of output for mesh coordinates of the source region in all datatransfers.

→SourceMeshTopol (integer)

This setting controls the level of output for mesh topology (elements and nodes) of the sourceregion in all data transfers.

→SourceData (integer)

This setting controls the level of output for the source data in all data transfers.

→TargetMeshCoords (integer)




This setting controls the level of output for mesh coordinates of the source region in all datatransfers.

→TargetMeshTopol (integer)

This setting controls the level of output for mesh topology (elements and nodes) of the sourceregion in all data transfers.

→TargetData (integer)

This setting controls the level of output for the target data in all data transfers.

The level of detail to include in debug output is controlled using one of the following integer valuesfor either the default or specific sections of output:

– 0: None

– 1: Level 1

– 2: Level 2

– 3: Level 3

– 4: Level 4

– 5: All Levels

Increasing values always generate more detailed output. Note, as well, that the output level settingsfor each of the mesh coordinates and topology, and transfer data control the number of lines of

output generated. Specifically, 10L lines of data will be written for an output level setting of L (forexample, 100 lines will be written for an output level of 2, or “Level 2”).

• IntermediateResultsFileOutput

This subsection is used to specify the frequency at which intermediate result files, which can be usedfor restarts, are written by the System Coupling service.

– FrequencyOption (integer)

Available options are 0 (every coupling step) and 1 (coupling step interval)

– StepInterval (integer)

The coupling step interval at which intermediate result files should be generated (Note that thisis valid only when FrequencyOption is set to Step Interval). For example, using a step intervalof 3, results will be generated at steps 3, 6, 9, ...

The following entry may be reported in the SCI file, but is not used by the System Coupling service:

• MappingSettings

Understanding the System Coupling Log File

The System Coupling Service log file (scLog.scl) provides key run time information and is dividedinto four blocks:



• start-up and executable information,

• coupled analysis setup information,

• solution details,

• and shut-down information.

The start time and date, command line information and executable details for the run appear as follows:

Run start time and date: 10:15:41, Sep 19 2014

Command line used to start this service:

C:\Program Files\ANSYS Inc\v160\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe -inputFile scInput.sci

==================================================================================================================================================================================================================| || ANSYS System Coupling Service || Version 16.0, Copyright 2014 || (Build Info. - 10:09:03, Sep 19 2014) || |==================================================================================================================================================================================================================

The command used to start the System Coupling service is given next as shown below:

Command line used to start this service: C:\Program Files\ANSYS Inc (Dev)\v160\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe

An echo of the SC service input file is provided next in the log file below the following header:

====================================================================== ====================================================================== | | | Summary of System Coupling Setup | | | ====================================================================== ======================================================================

The information generally found in this section includes unit system data (for example, MKS, and soon), as well as information relating to coupling (time versus coupling step), initialization (options suchas time value or initial coupling step), duration (for example, end time), and step size and the maxim-um/minimum number of iterations.

Note

When the coupling is defined by coupling step (and not by time), then time-related inform-ation (initial time, end time, or step size) is not displayed in this section of the log file, andonly step-related information is available (for example, initial step, number of steps, maximumand minimum iterations).

Summary of System Coupling Setup

Under this section of the log file, there are sub-blocks (for example, “Analysis Information”, “CouplingParticipant Information”, “Data Transfer Information”, “Execution Control Information”, “Setup Validation“and “System Coupling Co-Simulation Summary”). A brief description of these sub-blocks is providedbelow.




The Analysis Information section includes basic information about the coupling definition, the unitsystem, as well as time and step information.

======================================================================| Analysis Information |======================================================================

General : Analysis Type = Transient Unit System = MKS

Initialization : Option = Automatic

Step : Option = Step Size Size = 0.05 Minimum Iterations = 5 Minimum Iterations = 5

Duration : Option = End Time Time = 0.05

The Coupling Participant Information section includes information about each of the solvers connectedto the system coupling simulations (for example, internal name, type (either Co-Simulation or StaticData), units, and so on). Additional information for coupled regions and variables that appear in datatransfers is also displayed in this section of the log file. This additional information includes: the coupledname and type (for regions); and the variable name and physical type (for variables). This informationis not displayed for regions and/or variables that do not participate in data transfers. If such regions orvariables exist, a message is written to indicate that the related information has been omitted from thissection of the log file.

======================================================================| Coupling Participant Information (2) |======================================================================

+--------------------------------------------------------------------+| Participant: Fluent |+--------------------------------------------------------------------+

General : Unit System = MKS_STANDARD Type = CoSimulation Name = Fluent

Summary of Coupling Regions (1)Region : plate Internal Name = plate Type = Surface

Summary of Coupling Variables (2)Variable : Displacement Display Name Internal Name = INCD Physical Type = Length Variable : Force Display Name Internal Name = FORC Physical Type = Force

Summary of Base Units (9) Angle = radian ChemicalAmount = mol Current = A Length = m Luminance = cd Mass = kg SolidAngle = sr Temperature = C Time = s



+--------------------------------------------------------------------+ | Participant: External Data | +--------------------------------------------------------------------+

General : Unit System = SI Type = Static Data Name = Setup 2 File Path = external_load_data.xml

Summary of Coupling Regions (1) Region : File1 Internal Name = ExtDataReg_Setup 2_0 Type = Surface

Summary of Coupling Variables (1) Variable : Temperature1 Internal Name = ExtDataVar_Setup 2_0_1 Physical Type = Temperature

Summary above omits variables not used in data transfers.

Summary of Base Units (9) Angle = radian ChemicalAmount = mol Current = A Length = m Luminance = cd Mass = kg SolidAngle = sr Temperature = K Time = s

The Data Transfer Information section includes:

• Region and variable information for the source and target of each data transfer

• Data transfer options, such as the convergence criteria and target

• The under-relaxation factor

• Ramping option

======================================================================| Data Transfer Information (2) |======================================================================

+--------------------------------------------------------------------+| Data Transfer: Mechanical Displacement to Fluent |+--------------------------------------------------------------------+

Source : Mechanical Region = Mechanical Wall Display Name Variable = DISP Display Name

Target : Fluent Region = plate Variable = Displacement Display Name

General Information : Name = Mechanical Displacement to Fluent Execute Transfer At = Start Of Iteration Convergence Option = RMS Change In Data Target Value = 0.01 Under Relax. Factor = 0.25 Ramping = None

+--------------------------------------------------------------------+| Data Transfer: Fluent Force to Mechanical |+--------------------------------------------------------------------+




Source : Fluent Region = plate Variable = Force Display Name

Target : Mechanical Region = Mechanical Wall Display Name Variable = FORC Display Name

General Information : Name = Fluent Force to Mechanical Execute Transfer At = Start Of Iteration Convergence Option = RMS Change In Data Target Value = 0.01 Under Relax. Factor = 0.25 Ramping = Linear to Min. Iterations

The Execution Control Information section includes a summary of the sequencing of co-simulationparticipants, and requests for debug and intermediate result file output. Note that the debug and inter-mediate result output summaries are generated only if such output is requested. For example:

======================================================================| Execution Control Information |======================================================================

+--------------------------------------------------------------------+| Co-Simulation Sequence |+--------------------------------------------------------------------+

Sequence Index : 1 Fluent Solver

Sequence Index : 2 Mechanical Solver

+--------------------------------------------------------------------+| Debug Output |+--------------------------------------------------------------------+

General Output : Default = Level 1 Startup = None Participant Conn. = None Analysis Init. = None Solution Init. = None Convergence Checks = None Shutdown = None

Data Transfer Output : Default = Level 1 Source Coords. = None Source Topology = None Source Data = None Target Coords. = None Target Topology = None Target Data = None

+--------------------------------------------------------------------+| Intermediate Restart Data Output |+--------------------------------------------------------------------+

Output Frequency : Option = Step Interval Interval = 3

The Setup Validation section includes any warning or error messages that may have been generated.For example:



======================================================================| Setup Validation |======================================================================

+--------------------------------------------------------------------+| Warnings ( 1) |+--------------------------------------------------------------------+

1 ) Auto-Correction: The specified maximum iterations per step is less than the specified minimum iterations. The maximum iterations will be set to the minimum iterations.

+--------------------------------------------------------------------+| Errors ( 1) |+--------------------------------------------------------------------+

1 ) The solution sequence specified for the participant named 'Fluent' is not greater than zero. Adjust this (and other) sequence values appropriately.

The System Coupling CoSimulation Summary section includes a brief summary of the participants inthe co-simulation.

======================================================================| System Coupling CoSimulation Summary |======================================================================

Participant : Mechanical APDL Version/Build Info = Mechanical APDL Release 16.0 UP20130905 DISTRIBUTED WINDOWS x64 Version Participant : Fluent Version/Build Info = ANSYS Fluent 16.0.0

Solution

Next is the “Solution” block. Under it, the following information is provided.

====================================================================== ====================================================================== | | | Solution | | | ====================================================================== ======================================================================

The Solution block contains a Mapping Summary section:

+--------------------------------------------------------------------+ | MAPPING SUMMARY | +--------------------------------------------------------------------+ | Data Transfer | | | Diagnostic | Source Side | Target Side | +----------------------------------+----------------+----------------+ | Mechanical Displacement to Fluent| | | | Percent Nodes Mapped | N/A | 100 | | Fluent Force to Mechanical | | | | Percent Nodes Mapped | 100 | 100 | | Percent Area Mapped | 100 | 100 | +----------------------------------+----------------+----------------+

The current coupling step number and the current simulation time are reported as shown below. Thisinformation will be a part of a box that is repeated in the log file at the beginning of every couplingstep. It looks similar to the following:

+====================================================================+| COUPLING STEP = 1 SIMULATION TIME = 0.001 ||--------------------------------------------------------------------|| Solver | Solution Status |




| Data Transfer | || Diagnostics | Source Side Target Side |+====================================================================+

Note that if the simulation is defined only by steps (and not by time), then the log file output will onlypresent step-related information.

Next is another box that repeats every coupling iteration of every coupling step. It looks like:

+--------------------------------------------------------------------+| COUPLING ITERATION = 1 |+--------------------------------------------------------------------+| Fluent | Not yet converged... ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Mechanical Displacement to Fluent| Not yet converged... || Change:RMS | 1.00000e+000 1.00000e+000 ||--------------------------------------------------------------------|| Mechanical | Not yet converged... ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Fluent Force to Mechanical | Not yet converged... || Change:RMS | 1.00000e+000 1.00000e+000 |+--------------------------------------------------------------------+| COUPLING ITERATION = 2 |+--------------------------------------------------------------------+| Fluent | Converged ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Mechanical Displacement to Fluent| Converged || Change:RMS | 2.82982e-005 1.42982e-004 ||--------------------------------------------------------------------|| Mechanical | Converged ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Fluent Force to Mechanical | Converged || Change:RMS | 1.30000e-004 2.08200e-000 |+--------------------------------------------------------------------+

As indicated above, after every coupling iteration, the convergence status is given for each participant.Common participant status values are Converged and Not yet converged..., however, Diver-gence detected... and Status Unavailable could also be reported. Below the solver statusis a list of the data transfers for which the participant is the target, plus diagnostics used to evaluateconvergence of the data transfer. Any supplemental diagnostics (as described in the SC Log OutputControl Settings section in Understanding the System Coupling Input File (p. 58)) that have been re-quested are also included here.

Notes specific to the execution of a given coupling step will be reported under the final coupling iterationof the step. For example:

+====================================================================+ | NOTES | | * During this coupling step, the target variable, Convection | | Coefficient, was clipped for the data transfer: Upper HTC. | | * Intermediate result file written: scResult_01_000475.scr | +====================================================================+

Shutdown

Next is the “Shut Down” block under which the following information is included:

====================================================================== ====================================================================== | | | Shut Down | | | ====================================================================== ======================================================================

System Coupling Service shut down...



Run completed successfully.

The preceding output is generated under normal shutdown conditions. If a co-simulation participant(or the coupling service itself ) fails during the analysis, the normal shutdown output will be replacedby messages similar to the following:

+====================================================================+ | NOTICE | | An exception has occurred and has been transmitted to the coupling | | participants. These participants have been disconnected from the | | coupling service. | +====================================================================+

+====================================================================+ | System Coupling Exception | +====================================================================+ | Origin : Fluids Problem (Solution 1) | | Error Code : 2 | | Error Description : | | Fluent encountered fatal error after sync point Solve | +====================================================================+

System coupling run completed with errors.

The first block indicates that all co-simulation participants have been notified of the problem. Thesecond block indicates the origin (that is, the coupling participant) of the failure, and an error code anddescription. For additional information, see Troubleshooting Two-Way Coupled Analyses Problems (p. 73).





Best Practice Guidelines for Using System Coupling

This chapter presents ideas to facilitate the successful setup and execution of a coupled analysis viathe System Coupling infrastructure:

Building up a Coupled Analysis from Decoupled SystemsTroubleshooting Two-Way Coupled Analyses ProblemsImproving Coupled Analysis Stability

Building up a Coupled Analysis from Decoupled Systems

Coupling otherwise independent analysis systems often introduces additional non-linearity to thesolution and solution process. For this reason, it is strongly recommended that you verify that all ofyour constitutive analyses run independently before you systematically build up your one- and two-way coupled analyses.

The independent analyses executed prior to coupled analysis should attempt to replicate the effects ofthe coupled problem as closely as possible. For fluid-structure interaction problems, for example, thefluid-only analysis could include user-specified motion that approximately models the expected motion(or range thereof ) from the structural analysis. Similarly, the structure-only analysis could include a user-specified load that approximately models the expected load (magnitude and distribution) from thefluid analysis.

Prior to executing two-way coupled analyses, it is also strongly recommended that you execute a setof one-way coupled analyses. The benefits of building up coupled analyses this way include:

• Augmenting the fully decoupled analyses proposed above with a more accurate approximation of theinputs expected from the independent analysis

• Verifying the need for a two-way coupled analysis by assessing the sensitivity of the dependent analysisto inputs expected from the independent analysis

For fluid-structure interaction problems, for example, loads exported from the fluid-only analysis couldbe applied in the structure-only analysis. If, under these conditions, a significant deformation due tothe applied loads is observed, then a two-way coupled analysis may be appropriate. Note, however,that two-way coupled analyses are significantly more computationally expensive (by approximately anorder of magnitude) than one-way coupled analyses.

Execution of a two-way coupled analysis follows once fully decoupled and one-way coupled analysesare verified to run as expected and the need to execute a two-way coupled analysis is confirmed. Evenat this point, however, difficulties may be encountered during the execution of the two-way coupledanalysis due to the increased complexity of this problem. The following information will aid in debuggingsuch analyses.

Troubleshooting Two-Way Coupled Analyses Problems

Once any solution difficulties associated with executing fully decoupled and one-way coupled analyseshave been addressed, a two-way coupled analysis may be attempted. The information presented in this



section provides a summary of tools and strategies available to facilitate debugging two-way coupledanalyses. These focus on text based and graphical monitor output, and supplemental output for visual-ization in ANSYS CFD-Post.

For more information, see the following sections:Using Text-Based Monitor Output to Debug Coupled AnalysesUsing Graphical Monitor Output to Debug Coupled AnalysesUsing Supplemental Output to Debug Coupled AnalysesSupplemental Output for Diagnosing Mapping Problems

Using Text-Based Monitor Output to Debug Coupled Analyses

Text-based monitor output is contained in the System Coupling Log (SCL) file that is created in the rundirectory. Sections of the SCL file that are most relevant to the debugging process are identified below.If problems are encountered, you should carefully review all of these sections.

• Setup Validation: This section facilitates review and verification of the input settings made for the systemcoupling service. These inputs are validated by the coupling service, and both warnings and errors generatedduring validation are reported here. Any automatic corrections applied to the inputs are listed with validationwarnings.

• Mapping Summary: This section summarizes the extent to which the source and target regions associatedwith each data transfer are correctly mapped onto one-another. Under normal conditions, diagnostics shouldreport a nearly perfect mapping. Less than perfect mappings should be critically considered for their validity.

• Coupled Solution Convergence History: This section summarizes the convergence of both the couplingparticipants and the data transfers that target each of the participants. It is strongly recommended thatsufficient coupling iterations be executed, per step, to ensure that the field equations solved by all couplingparticipants and the data transfers defined for the coupled analysis converge fully. Note, however, that thecoupling service will advance to the next coupling step, regardless of convergence, once the maximumnumber of coupling iterations per step has been executed. You are advised to identify and understand allreasons for poor convergence of coupling participants or data transfers.

• Error Messages: Fatal errors are reported, as they occur, in the log output. These errors may have originatedeither within the coupling service itself or within any of the coupling participants. When such an error occurs,output from the service and all participants should be critically reviewed.

• Shutdown Reporting: Under normal conditions, the end of the log output generated by the coupling servicereports whether or not the coupled analysis completed successfully. When the analysis does not completesuccessfully, additional information is provided as to what may have caused the problem.

For more information on the content of the SCL file see System Coupling Service Log File (scLog.scl_,scLog_##.scl) (p. 57). Note, as well, that supplemental debug output can also be written to the SCLfile to facilitate debugging. This output is generated by adding debug output specifications to the systemcoupling setup.

Similar output files often exist (either by default or by user request) for the coupling participants. Forexample, the ANSYS Fluent solver can generate a text based transcript file and the ANSYS MechanicalAPDL solver can generate a text based output file. Please refer to Supported System Couplings (p. 3)for more information regarding the text based monitor output that they can generate.



Using Graphical Monitor Output to Debug Coupled Analyses

Graphical monitor output is provided in the form of charts within the System Coupling user interface.This output is most useful to quickly identify convergence problems. Once such problems are identified,a review of text monitor output is usually appropriate.

Data that can be displayed in the system coupling chart includes:

• Data transfer convergence and diagnostics, corresponding to the numerical data written to the systemcoupling log file.

• Co-simulation participant convergence, most often corresponding to the (normalized) field equation con-vergence values from the solvers.

Each co-simulation participant provides whatever convergence data it can. Different amounts of datamay be available for charting from each co-simulation participant.

Convergence data is collected from a co-simulation participant at the end of that participant’s solutionduring a given coupling iteration. In particular, the set of solver substep and solver iteration convergencedata corresponding to the coupling iteration are updated all at once. If rapid divergence and failure ofa solver occurs during a given coupling iteration, this information will not be included in the chartedoutput for that iteration.

Using Supplemental Output to Debug Coupled Analyses

At your request, the system coupling service will generate output that supplements the text-based andgraphical monitor output. As discussed below, the supplemental output facilitates the diagnosis ofmapping problems.

Note that visualization of multi-dimensional features (for example, mesh interface regions) of a problemcurrently requires the use of an external viewer such as the Results component system (that is, CFD-Post) in the ANSYS Workbench environment.

Supplemental Output for Diagnosing Mapping Problems

Supplemental output, which is specifically aimed at diagnosing mapping problems, includes:

• Data transfer source and target interface meshes.

• A scalar field indicating (un)mapped nodes.

To enable this output, create and set the expert setting DumpInterfaceMeshes to the value CFDPost.When this setting is made, one user surface definition file (in a comma separated value, CSV, format)will be generated by the coupling service during the mapping process for each source and target foreach data transfer. This data is used in the CFD-Post application either using the "Import Surface or LineData" functionality or by creating a user surface location directly from the definition file(s).

Once the user surfaces associated with the source and target interface meshes are created in CFD-Post,they may be visually examined for consistency (for example, if the source and target surfaces or nodesare coincident). The surface may be colored by the ‘Unmapped’ variable, which will report values of 0and 1 for unmapped and mapped nodes, respectively. This corresponds to blue and red, respectively,using the default color map.



Troubleshooting Two-Way Coupled Analyses Problems

Unmapped nodes may also be visualized by inserting a point location with the Method set to VariableMinimum for the ‘Unmapped’ variable on the surface of interest. Attributes of the plotted points, suchas the symbol shape and size, may be edited to facilitate visualization.

Improving Coupled Analysis Stability

There are several ways to improve the stability of a coupled analysis:Data Transfer RampingParticipant Solution StabilizationCo-Simulation Participants Sequencing

Data Transfer Ramping

In some cases, applying the full magnitude of data on the target side of data transfer interface will ini-tiate oscillatory convergence or even divergence within and between the coupled co-simulation parti-cipants. For this reason, the target side data may be ramped from the final value observed in the previouscoupling step (or zero during the first coupling step) to the full magnitude during the initial couplingiterations within the current step.

For more information about ramping behavior and controls, see Data Transfers (p. 14). For more inform-ation about the algorithm used for System Coupling’s ramping, see Ramping Algorithm (p. 53).

Participant Solution Stabilization

Solution instabilities that manifest as a very rapid divergence of the coupled analysis may arise if agiven coupling participant is particularly sensitive to data obtained from another participant. In thesecases, it may be advantageous to use various solution stabilization algorithms that have been imple-mented in the target participant.

For an example of participant solution stabilization, refer to the dynamic mesh system coupling solutionoptions used in ANSYS Fluent, described in System Coupling Motion in the Fluent User's Guide.

Co-Simulation Participants Sequencing

In general, the driver of the physical problem should be processed first (that is, given a lower sequenceindex). If, in a fluid-structure interaction (FSI) simulation, the fluid flow (such as air flow around a wing)causes the structure (that is, the wing) to deform, then the fluid analysis should be first in the processingsequence.

The System Coupling infrastructure allows the co-simulation of multiple coupling participants. In manycases, the execution (for example, solve) sequence of the co-simulation participants is inconsequential.In some cases, however, the sequence may affect solution stability and/or the time required to executethe complete coupled analysis.

Note

To improve solution stability, sequential solutions are used by default. To facilitate syn-chronization of interface geometry, participants that consume geometrical or mesh de-formations (e.g., the Fluids solver in a Fluid Structure Interaction analysis) are executedlast.



Controlling Participant Sequencing

Participant sequencing controls the order in which co-simulation participants collect data (as prescribedby defined data transfers) and execute their part of the coupled analysis. Ordering is specifically controlledby assigning a sequence index to each of the co-simulation participants. Participants with the smallestsequence index are processed first. If two (or more) participants are assigned the same sequence index,they are processed simultaneously (that is, required data is first collected from other participants, andthen the participants all execute (for example, solve) simultaneously.

Care is taken to ensure that the geometry and mesh are properly synchronized at the end of eachcoupling step for all co-simulation participants. This is required to ensure consistency during post-pro-cessing and during restarts. An extra ‘partial’ coupling iteration reprocesses all participants that aretargets of deformation or motion-related data transfers. An extra partial iteration is executed once afterall convergence targets are met or the maximum number of coupling iterations for the step is realized.A warning that extra partial iterations will be performed is provided in the validation output that followsthe setup summary in the System Coupling Service Log File (scLog.scl_, scLog_##.scl) (p. 57).

When an extra 'partial' coupling iteration is used to properly synchronize the interface geometry andmesh, there will be no noticeable change in the geometry and mesh during the first coupling iterationof the subsequent step. In this case, the system coupling chart output will have near-zero values forthe change in motion for the related data transfer values.

Using Sequencing to Reduce Coupled Solution Execution Time

As noted above, all co-simulation participants that share the same sequence index will collect data andexecute their respective parts of the coupled analysis at the same time. This is a way of parallelizingthe coupled solution process and potentially reducing the overall execution time of the coupled analysis.However, convergence difficulties (for example, more coupling iterations per step) and possible diver-gence may occur when multiple participants run simultaneously. This is because each participant in thegroup that is solved simultaneously collects and uses less up-to-date information from other participants.The stronger the physical coupling between each participant is, the more likely convergence difficultieswill be encountered if the participants are processed simultaneously.



Improving Coupled Analysis Stability


Tutorial: Oscillating Plate with Two-Way Fluid-Structure Interaction

In this tutorial you will learn how to solve a Fluid-Structure Interaction (FSI) case. You will model struc-tural deformation in a fluid using System Coupling to coordinate the ANSYS Mechanical and ANSYSFluent solvers.

DetailsFeatureComponent

Transient StructuralAnalysis SystemsANSYS Workbench

Fluid Flow (Fluent)

System CouplingComponent Systems

Defining new materialsEngineering Data

ImportGeometryDesignModeler

MeshingMechanical

Defining the physics

Named Selections

Coupled analysis restart

Coupled analysis batchexecution from commandline

MeshingMeshing

Defining the physicsANSYS Fluent



Defining the couplingSystem Coupling



VectorPlotsCFD-Post

Animation

This tutorial includes:Overview of the Problem to SolveCreating the ProjectOptional: Preparing for a Command-line RunAdding Analysis Systems to the ProjectAdding a New Material for the ProjectAdding Geometry to the ProjectDefining the Physics in the Mechanical Application



Setting up your Fluid AnalysisDefining and Running the Coupling in the System Coupling ApplicationViewing Results in CFD-PostSetting Up and Executing a Coupled Analysis Restart from WorkbenchExecuting the Coupled Analysis from the Command Line

Note

In the main flow of the tutorial, you use the user interface to completely solve the simulation.However, at a series of points during the tutorial you have optional instructions that producefiles that will enable you to solve the simulation from the command line. The steps relatedto this are:

1. Optional: Preparing for a Command-line Run (p. 82)2. Preparing for a Command-Line Run of the Structural System (p. 90)3. Preparing for a Command-Line Run of the Fluent System (p. 97)4. Preparing for a Command-Line Run of the System Coupling System (p. 100)5. Executing the Coupled Analysis from the Command Line (p. 105)

If you do not want to solve the simulation from the command line, you may ignore thosesteps.

Overview of the Problem to Solve

This tutorial uses an example of an oscillating plate within a fluid-filled cavity to demonstrate how toset up and run a simulation involving a two-way coupled analysis in ANSYS Workbench.

A thin plate is anchored to the bottom of a closed cavity filled with fluid (air), shown in Figure 12: Di-mensions of the oscillating plate case (p. 80). There is no friction between the plate and the side of thecavity. An initial pressure of 100 Pa is applied to one side of the thin plate for 0.5 s to distort it. Oncethis pressure is released, the plate oscillates back and forth to regain its equilibrium, and the surroundingair damps this oscillation. You will simulate the plate and surrounding air for a few oscillations to beable to observe the motion of the plate as it is damped.

Figure 12: Dimensions of the oscillating plate case



To simulate this case, you will set up a two-way Fluid-Structure Interaction (FSI) analysis. You willmodel the motion of the oscillating plate using the Mechanical application’s Transient Structuralanalysis system. You will model the motion of the fluid in the closed cavity using the Fluent application’sFluid Flow (Fluent) analysis system. The two analyses are solved at the same time with the SystemCoupling system coordinating the solution process as well as the data transfers between the two ana-lysis systems.

The two-way coupling involves two data transfers:

• Force data from the motion of the air is received by the Transient Structural analysis system as it solvesthe structural behavior over time.

• Displacement data from the motion of the plate is received by the Fluid Flow (Fluent) analysis system asit solves the fluid behavior over time.

The oscillation of the plate is dependent on time, and so you need to choose appropriate time valuesfor the coupled transient analysis:

• Time duration is the total time observed in the analysis. In this analysis, you will set the time duration to be10 s, which is enough time to observe the plate oscillating a few times. With this time duration, you will notmodel the full damping back to the plate’s equilibrium. When setting up a transient analysis, make sure thatyou choose a time duration that will allow you to observe the behavior of interest in your system.

• Time step is the size of the time increments that you are solving within your transient analysis. In this ana-lysis, you will set the time step to be 0.1 s, which is fine enough to observe the oscillations to a reasonabledegree. When setting up a transient analysis, make sure you choose a time step that works for the physicsyou are solving. Too large a time step will miss behavior of the system, and too small a time step will becomputationally expensive.

Creating the Project

Create the project by setting up Workbench and importing the project files:

1. Start ANSYS Workbench:

• To launch ANSYS Workbench on Windows, click the Start menu, then select All Programs > ANSYS 16.0> Workbench 16.0.

• To launch ANSYS Workbench on Linux, open a command line interface and enter the path to runwb2.For example:

~/ansys_inc/v160/Framework/bin/Linux64/runwb2

The Project Schematic appears with an Unsaved Project. By default, ANSYS Workbench is configuredto show the Getting Started dialog box that describes basic operations in ANSYS Workbench. Clickthe [X] icon to close this dialog box.

2. Create a directory where you will store your project (this is your working directory). For example, underMy Documents, create a directory named SystemCouplingOscillatingPlate.

3. Select File > Save or click Save .

4. Select the path to your working directory to store files created during this tutorial.




5. Under File name, type SystemCouplingOscillatingPlate and click Save.

The project files and their associated folder locations appear under the Files view. To make theFiles view visible, select View > Files from the main menu of ANSYS Workbench.

6. This tutorial uses the geometry file,oscillating_plate.agdb, for setting up the project. To accesstutorials and their input files on the ANSYS Customer Portal, go to http://support.ansys.com/training.

Copy the supplied geometry file, oscillating_plate.agdb, to the user_files directorythat is in the SystemCouplingOscillatingPlate_files directory.

By working with a copy of the geometry file in your working directory, you prevent accidentalchanges to the original geometry file.

Optional: Preparing for a Command-line Run

This tutorial runs from within Workbench. However, you also have the option of taking files createdfrom applications running in Workbench and performing a second system coupling run from a commandline. If you want to try this alternative, follow the instructions below to prepare the locations where thissecond system coupling run will be performed. As you work through the tutorial in Workbench, youwill be prompted to add source files from the applications running in Workbench to the directories youcreate here.

To prepare a directory structure for executing the analysis from a command line:

1. Create a high-level directory named SystemCouplingOscillatingPlate_CmdLine. This directoryshould be a sibling to SystemCouplingOscillatingPlate.

2. In the SystemCouplingOscillatingPlate_CmdLine directory, create subdirectories within whichthe Mechanical APDL, Fluent, and System Coupling service executables will be run. Name these subdirect-ories:Structural_CmdLine,FluidFlow_CmdLine, and Coupling_CmdLine.

Adding Analysis Systems to the Project

You are doing a two-way FSI analysis by coupling two analysis systems: a Transient Structural systemand a Fluid Flow (Fluent) system. You will use the System Coupling system to couple the other twosystems and to coordinate the solution execution.

To add these three systems to your Workbench project:

1. From the Analysis Systems toolbox located on the left side of the ANSYS Workbench window, select theTransient Structural template. Double-click the template, or drag it onto the Project Schematic to createa standalone system.

A Transient Structural system is added to the Project Schematic, with its name selected and readyfor renaming.

2. Type in the new name,Structural, to replace the selected text. In this tutorial,“Structural system” willbe used to refer to the Transient Structural system.

If you missed seeing the selected text, right-click the first cell in the system and select Renamefrom the context menu. You will then be able to edit the name.



http://support.ansys.com/training

3. Drag a Fluid Flow (Fluent) analysis system on top of the Structural system’s Geometry cell (A3) and dropit there.

A Fluid Flow (Fluent) system, coupled to the Structural system, is added to the Project Schematic.This Fluid Flow (Fluent) system is connected to the Structural system through the Geometry cell(A3 to B2), and so both of these systems will share the same geometry.

4. Change the name of this system to Fluid. In this tutorial,“Fluid system” will be used to refer to theFluid Flow (Fluent) system.

5. Expand the Component Systems toolbox, drag a System Coupling system and drop it to the right ofthe Fluid Flow (Fluent) system.

6. Drag the Structural system's Setup cell (A5) and drop it on the System Coupling system’s Setup cell (C2).

7. Drag the Fluid system's Setup cell (B4) and drop it on System Coupling system’s Setup cell (C2). Nowall three systems are connected for a two-way FSI analysis.

8. Save the project.

The Project Schematic should appear as shown in Figure 13: System Coupling of Transient Structuraland Fluid Flow (Fluent) Systems (p. 83).

Figure 13: System Coupling of Transient Structural and Fluid Flow (Fluent) Systems

The Structural and Fluid systems have various cells. The icons on the right side of each cell providesvisual indications of a cell's state at any given time. In your current Project Schematic in Workbench(shown in Figure 13: System Coupling of Transient Structural and Fluid Flow (Fluent) Systems (p. 83)),

most cells appear with a blue question mark ( ), indicating that cells need to be set up before continuingthe analysis. As these cells are set up, the data transfer occurs from top to bottom. See UnderstandingCell States for a description of various cell states.

Now that your project systems are in place, you can start working through your analysis. Your currentproject systems enables you to perform your analysis by:

• adding a new material,

• sharing the geometry,

• setting up the physics in the Structural system,



Adding Analysis Systems to the Project

• setting up the physics in the Fluid system,

• defining and running the coupling in the System Coupling system, and

• viewing the results in CFD-Post.

Adding a New Material for the Project

In the Project Schematic, the Structural system’s Engineering Data cell (A2) appears in an up-to-datestate because default material is already available for the project. You will use material for the oscillatingplate that is not in the default material available, and so you need to update this cell by adding thisnew material to the Engineering Data.

The case requires a new material with properties that allow it to oscillate when pressure is applied. Youwill create a new material named Plate, define its properties to be suitable for oscillation, and set it asthe default material for the analysis.

1. On the Project Schematic, double-click the Engineering Data cell (A2) in the Structural system.

Engineering Data opens in a new tab in Workbench. The Outline and Properties views are amongthe views that appear.

2. In the Outline of Schematic A2: Engineering Data view, click the empty row at the bottom of the tableto add a new material for the project. Type in the name Plate.

When you click away from that cell, Plate is created and appears with a blue question mark, indic-ating that its properties need to be defined.

3. From the Toolbox on the left, expand Physical Properties. Select Density and drag it onto the cell con-taining Plate (A4) in the Outline of Schematic A2: Engineering Data view. If the toolbox is not visibleby default, select View > Toolbox to make it visible.

Density is added as a plate property in the Properties of Outline Row 4: Plate view, as shown inthe following figure.



4. In the Properties of Outline Row 4: Plate view, set the Value of Density (B2) to 2550 kg m^-3. Do nottype in units.

5. In the toolbox under Linear Elastic, drag Isotropic Elasticity onto Plate (A4) in the Outline of SchematicA2: Engineering Data view.

Isotropic Elasticity is added as the plate property in the Properties of Outline Row 4: Plate view.

6. In the Properties of Outline Row 4: Plate view, expand Isotropic Elasticity by clicking the plus sign.Now set Young’s Modulus to 2.5e06 [Pa] and Poisson’s Ratio to 0.35. Do not type in units.

The desired plate data is created and is available to the remaining cells in the Structural system.

The next step is to set Plate as the default material for the analysis as outlined below:

1. In the Outline of Schematic A2: Engineering Data view, under Material, right-click Plate (A4) and selectDefault Solid Material For Model.

2. From the main menu, select File > Save to save material settings to the project.

3. Close the Engineering Data tab to return to the Project Schematic.

Adding Geometry to the Project

You will add geometry to your project by importing an existing DesignModeler file. Once you add thegeometry, it will be shared between the Structural and Fluid systems because you have connected theirgeometry cells in the Project Schematic. All of the geometry parts have to be unsuppressed at this pointin your project so that they are available for use later in the Structural and Fluid systems.

1. On the Project Schematic, right-click the Structural system’s Geometry cell (A3) and select ImportGeometry > Browse.




2. In the Open dialog box, browse to your working directory, select SystemCouplingOscillating-Plate_files > user_files > oscillating_plate.agdb from your working directory, and clickOpen.

3. In the Structural system, double-click the Geometry cell (A3) to edit the geometry using DesignModeler.

The DesignModeler application opens in a separate window.

4. In DesignModeler’s Tree Outline on the left, expand the branch 2 Parts, 6 Bodies to see all of the bodiesthat compose the geometry. The one solid body is listed, and under Part are the five fluid bodies. Ensurethat all of these bodies are already unsuppressed (they should all have small green check marks).

5. The geometry is set up for the project. Save any changes by selecting File > Save Project from the mainmenu in DesignModeler, and then select File > Close DesignModeler to return to the Project Schematic.

The updated geometry is now available for both the Structural and Fluid systems.

Later in the tutorial, when you generate the structural mesh, the fluid bodies will first be suppressed.Similarly, when you generate the fluid mesh, the solid body will be suppressed. You will suppress thesebodies from within the Mechanical and Meshing applications, so no further changes are needed inDesignModeler.

Note

Because the Structural system’s Geometry cell (A3) shares its content directly with the Fluidsystem’s Geometry cell (B2), you can edit the geometry only through the Structural system’sGeometry cell (A3).

Defining the Physics in the Mechanical Application

In the Mechanical application, you are setting up the structural analysis and defining the coupling inter-face. You will not solve the structural analysis from the Mechanical application because you will usethe System Coupling system to solve both structural and fluid systems at the same time.

When setting up your own two-way coupled analysis, it is a best practice to set up and solve thestructural analysis within the Mechanical application before continuing with your coupled analysis. Ifissues occur within your structural system, the isolated analysis is easier to troubleshoot than the morecomplex coupled analysis.

The structural Geometry cell (A3) is up-to-date, and so you start your setup by generating the structuralmesh. This section describes the step-by-step definition of the structural physics:

Generating the Mesh for the Structural SystemAssigning the Material to the GeometrySetting the Basic Analysis ValuesInserting LoadsPreparing for a Command-Line Run of the Structural SystemCompleting the Setup for the Structural System

Generating the Mesh for the Structural System

Generate the mesh for the Structural system directly in the Mechanical application:



1. On the Project Schematic, double-click the Structural system’s Model cell (A4) to open the Mechanicalapplication.

The Mechanical application opens in a separate window.

2. In Mechanical’s Outline on the left, expand Geometry to see the two geometries, solid and Part.

3. For the structural analysis, you need to generate the mesh for only the solid body. To do this, you needto first suppress the Fluid bodies.

Right-click the Part geometry (which contains all of the fluid bodies), and select Suppress Body.

The fluid bodies are now suppressed and their status changes to an x mark. You now will see only

the solid body in the Graphics view. Click Zoom to Fit to view the entire model in the Graphicsview.

4. You will define the mesh by marking divisions on the edges of the solid. These divisions will be used asguides for the mesh creation:

a. Click Edge .

b. Click an edge that lies parallel to the X axis.

c. In the Outline, right-click Mesh and select Insert > Sizing.

d. Beside Type, select Number of Divisions from the drop-down menu.

e. Beside Number of Divisions, select 1.

5. Repeat steps a to d to create 10 divisions on an edge that is parallel to the Y axis and 4 divisions on anedge that is parallel to the Z axis. To summarize:

Number of DivisionsEdge Direction

1X axis

10Y axis

4Z axis

6. In the Outline, right-click Mesh and select Generate Mesh from the shortcut menu.

A hex mesh is generated on your solid body.

Assigning the Material to the Geometry

When you defined the Plate material, you set it to be the default for your solid body. In the Mechanicalapplication, you can see that this material is set correctly.

1. In the Mechanical’s Outline on the left, select Project > Model > Geometry > solid.

2. In the Details of “solid”, ensure that Material > Assignment is set to Plate. Otherwise, click the materialname and use the arrow that appears to make the appropriate change.




Setting the Basic Analysis Values

You now need to set up information about the transient analysis’ time steps, which are the basic ana-lysis values needed for the transient structural analysis.

The time duration (10 s) is chosen so that the plate oscillates a few times during the analysis. A singlesubstep is used per coupling iteration. The coupling step size of 0.1s (which is also the size of the iter-ations) will be defined later in System Coupling.

These time settings are dependent on the physics that you are observing, including the material prop-erties of the plate. When setting your own transient analysis, make sure that you choose time settingsappropriate to the physics you are solving.

1. In the Mechanical application’s Outline view, select Project > Model > Transient > Analysis Settings.

The details of Analysis Settings appear in the Details of “Analysis Settings” below the Outlineview.

2. In the Details of “Analysis Settings”, specify the following settings under Step Controls (do not typeunits next to the time values):

1. Set Step End Time to 10.

2. Set Auto Time Stepping to Off.

3. Set Define by to Substeps.

4. Set the Number of Substeps to 1.

Inserting Loads

The loads applied for the structural analysis are equivalent to the boundary conditions in a fluid analysis.In this section, you will set the following loads and interface:

• a fixed support on the bottom of the plate

• a fluid-solid interface where the plate interacts with the fluid

• a pressure load on one side of the plate, to start the oscillation

On the surfaces of the plate that lie coincident with the symmetry planes, you will not set a load. Withno load set, the default of an unconstrained condition will be applied on these two surfaces. For thisparticular case, this unconstrained condition is a reasonable approximation of the frictionless supportthat would otherwise be applied.

Defining the Fixed Support

The fixed support is needed to hold the bottom of the thin plate in place. Set up the fixed support:

1. Right-click Transient in the Outline view, and select Insert > Fixed Support from the shortcut menu.



2. Rotate the geometry using the Rotate button so that the bottom (low-y) face of the solid is visible,

then select Face and click the low-y face.

That face is highlighted to indicate the selection.

3. In the Details of “Fixed Support” view, click Apply beside Geometry to set the fixed support.

If the Apply button is not visible, select Fixed Support in the Outline view and, in the Detailsview, click the text next to the Geometry setting to make the Apply button reappear.

The text next to the Geometry setting changes to 1 Face.

Defining the Fluid-Solid Interface

The fluid-solid interface defines the interface between the fluid in the Fluid system and the solid in theStructural system. Data will be exchanged across this interface during the execution of the simulation.

When setting up your structural system for a coupled analysis, you need to define this interface on regionsin the structural model that will receive force data from the Fluid system.

1. In the Outline view, right-click Transient and select Insert > Fluid Solid Interface from the shortcutmenu.

2. Using the same face-selection procedure described earlier in Defining the Fixed Support (p. 88), selectthe three faces of the geometry that form the interface between the structural model and the fluidmodel (low-x, high-y and high-x faces). Hold down Ctrl to be able to select multiple faces.

3. In the Details of “Fluid Solid Interface”, beside Geometry, click Apply.

The text next to the Geometry setting changes to 3 Faces.

Note that this load (fluid-solid interface) is automatically given an Interface Number of 1.

Defining the Pressure Load

The pressure load on one side of the plate provides the initial pressure of 100 Pa for the first 0.5 s ofthe simulation. This pressure to the plate starts the oscillation. It is defined using tabular data.

1. In the Outline view, right-click Transient in the tree view and select Insert > Pressure from the shortcutmenu.

2. In the Viewer, select the low-x face. In the Details of “Pressure” view beside Geometry, click Apply.

The text next to the Geometry setting changes to 1 Face.

3. In the Details of “Pressure” view, click the cell next to Magnitude, and using the arrow that appears,select Tabular.

The Tabular Data view appears on the bottom right of the Mechanical application window. Thetimes of 0 s and 10 s are the beginning and end of your analysis, based on the time duration (10s) that you specified earlier.

4. In Tabular Data, set a pressure of 100 Pa in the table row corresponding to a time of 0. Do not type inunits.




5. You now need to add two new rows to the table. Do this by typing the new time and pressure data intothe empty row at the bottom of the table. Notice that the rows are automatically re-ordered based onthe time value. Add the data from Table 4: Tabular Data for Step Pressure Load (p. 90).

Table 4: Tabular Data for Step Pressure Load

Pressure (Pa)Time (s)

1000

1000.5

00.51

010

You now have tabular data similar to a step function for your pressure, with 100 Pa applied for 0.5s. The step function is displayed in the graph to the left of the table.

6. The settings for the structural physics are now complete. Save these settings by selecting File > SaveProject from Mechanical’s main menu.

7. If you do not intend to execute a command line run using the set up from the Mechanical system, proceedto Completing the Setup for the Structural System (p. 91). If you do intend to execute a command linerun, continue with the next section.

Preparing for a Command-Line Run of the Structural System

If you intend to execute a command-line run using the set up from the structural system:

1. From the Mechanical application, select Tools > Write Input File.

2. Specify the path and APDL Input File (SystemCouplingOscillatingPlate_CmdLine\structur-al.dat) that you will use later.

Tip

The Write Input File option is available only if you have Transient (A5) selected in theOutline tree.

Note

Though out of the scope of this tutorial, below is information about augmenting yourstructural setup, and transferring the structural setup from the Mechanical application to theMechanical APDL application.

• In some cases, you may need to augment your structural setup in the Mechanical APDL application.If this is the case, then open that application and select File > Read Input From to choose the.dat file created by Mechanical. Once the .dat file has been read, make your setup modificationsand write a Mechanical APDL Database file using File>Save As Jobname.db or File >Save As.Starting the Mechanical APDL solver from the created database file is explained later in the tu-torial.



• Transferring the structural setup from the Mechanical application to the Mechanical APDL applic-ation is facilitated in ANSYS Workbench. To do this, right-click the Mechanical system's Setupcell (A5), and select Transfer to New > Mechanical APDL. Once the new Mechanical APDLsystem is introduced, update the upstream Mechanical system's Setup cell (A5). The setup willbe read into the Mechanical APDL user interface by right-clicking that system's Analysis cell andselecting Edit in Mechanical APDL.

Completing the Setup for the Structural System

On the Project Schematic, the Structural system’s Setup cell (A5) appears in an update-required state.To complete the setup in the Structural system, you need to ensure that all the data is in the right statein the Project Schematic.

1. In the Structural system, right-click the Setup cell (A5) and select Update from the shortcut menu.

The status of the Setup cell changes to up-to-date. All cells in the Structural system down to theSetup cell should now appear in an up-to-date state.

2. From the main menu, select File > Save to save the project.

The set up for the Structural system is complete. Remember that you will not solve the structural ana-lysis from the Mechanical application because you are using the System Coupling system to solve bothStructural and Fluid systems at the same time. In the next section, you will set up the Fluid system.

Setting up your Fluid Analysis

You will use the Fluent application to set up your Fluid system, but first you need to generate the meshusing the Meshing application. The fluid Geometry cell (B2) is up-to-date because it shares the geometrywith the structural analysis, and so you start your Fluid system’s setup with creating a mesh.

Generating the Mesh for the Fluid System

You will generate a mesh for the Fluid system using the Meshing application. For this geometry, youwill use a swept mesh across the x-y plane, creating a hex mesh with a depth of one element.

1. In the Project Schematic, double-click the Fluid system’s Mesh cell (B3) to open the Meshing application.

The Meshing application appears in a separate window.

2. In the Meshing application’s Outline view on the left, expand Geometry to see the two geometries, solidand Part.

3. For the fluid analysis, you need to generate the mesh for only the fluid bodies. To do this, you need tofirst suppress the structural body.

Right-click solid and select Suppress Body

The solid body is now suppressed and its status changes to an x mark. You now will only see thefluid bodies in the Graphics view.

4. In the Outline on the left, click Mesh. In the Details of “Mesh” below, under Defaults, notice that thePhysics Preference is set to CFD and Solver Preference is set to Fluent.




5. Now you need to define sweep as the meshing method, and set up all of the information that the sweepmethod needs:

a. In the Outline, right-click Mesh and select Insert > Method.

Automatic Method will appear under Mesh

b. Click Body , and then select all five fluid bodies in the Graphics view. Use the Ctrl key to selectmultiple bodies. Note that the fifth fluid body is very thin, and is above the plate.

c. With all five bodies selected, in the Details of “Automatic Method” – Method, beside Geometryclick No Selection. Click the Apply button that appears.

The text next to Geometry changes to 5 Bodies.

d. Under Definition, set Method to Sweep.

Notice that in the Outline above, under Mesh, the method is now renamed to Sweep Method.

e. In the Details of “Sweep Method” – Method, next to Src/Trg Selection, click Automatic. Using thearrow that appears, select Manual Source.

Manual Source enables you to dictate which surfaces are used as the source for the sweepmeshing. Source is highlighted, indicating that information about which surfaces to use isneeded.

f. Select Face , then Ctrl-select all five fluid faces on one of the walls in the x-y-plane (either side ofthe wall will work).

g. In the Details view, beside Source, click No Selection. Click the Apply button that appears.

The text next to Source changes to 5 Faces.



h. Set Free Face Mesh Type to All Quad so that all of the mesh elements are quadrilateral.

i. Next to Sweep Num Divs, set the value to 1.

j. In the Outline above, click Mesh. In the Details of “Mesh”, expand Sizing and set Min Size to 0.06and Max Face Size to 0.2. These settings control the size of the mesh elements that will be generated.

6. Now that all of the settings for your swept mesh are complete, you need to generate the mesh. In theOutline, right-click Mesh and select Update.

The swept mesh that you have defined is now generated for your fluid bodies.

7. Select File > Save Project, and then File > Close Meshing to close the Meshing application.




Defining the Physics in the ANSYS Fluent Application

In the Fluent application, you are setting up the fluid analysis, and defining the coupling interface. Youwill not solve the fluid analysis from the Fluent application because you are using the System Couplingsystem to solve both structural and fluid systems at the same time.

When setting up your own two-way coupled analysis, it is a best practice to set up and solve the fluidanalysis before continuing with your coupled analysis. If issues occur within your fluid system, the isolatedanalysis is easier to troubleshoot than the more complex coupled analysis.

This section describes the step-by-step definition of the fluid physics:Adding the Solution Setup SettingsDefining the Dynamic MeshAdding the Solution SettingsPreparing for a Command-Line Run of the Fluent System

Adding the Solution Setup Settings

You now need to open your analysis in the Fluent application, set the Fluid analysis to be transient,and add material to the fluid geometry.

1. In the Project Schematic, double-click the Fluid system’s Setup cell (B4) to open the Fluent application.

2. The Fluent Launcher opens in a new window. Under Options, select Double Precision.

3. Use the remaining default options (3D and serial), and click OK to close the Fluent Launcher.

The Fluent application opens in a new window, and the mesh file is automatically loaded.

4. On the left, select Setup > General. Under Time, click the Transient option.

5. On the left, select Setup > Materials > Air to assign material to your geometry. Click the Create/Editbutton, and in the dialog box that appears, for Density (kg/m3) type 1 and Viscosity (kg/m-s) type 0.2.Do not type units.

Click Change/Create to save these changes, and then click Close.

6. Under Setup > Models, note that by default, the viscous model is laminar and the energy model is turnedoff. No changes are needed to these settings.

Defining the Dynamic Mesh

A dynamic mesh is needed for any coupled analysis where a system receives displacements. In this tu-torial, the plate is oscillating back and forth, and the dynamic meshing settings determine how themesh of the fluid bodies react to this deformation of the moving structural body.

The mesh on the fluid-structural interface is static, so as the fluid mesh is modified to accommodatethe deformation in the transient system, the mapping on this coupling interface stays consistent.

Set up the dynamic mesh:

1. On the left, select Setup > Dynamic Mesh.

2. Check the Dynamic Mesh option in the panel. The settings for Dynamic Mesh are now available.



3. Under Mesh Methods, Smoothing is checked by default. Click the Settings button to specify the settingsfor the smoothing used.

The Mesh Method Settings dialog box appears.

a. On the Smoothing tab, set Method to Diffusion.

b. For the Diffusion Parameter, type 2. Click OK to close the dialog box.

4. Under Dynamic Mesh Zones, click Create/Edit to specify which zones in your geometry will have dynamicmeshing.

The Dynamic Mesh Zones dialog box appears.

5. Define the dynamic mesh settings needed for the surface “symmetry1”, which is the wall in the x-y planethat goes through the origin. This surface will be affected by the solid body’s displacement, and its meshneeds to be able to deform.

a. In the Dynamic Mesh Zones dialog box, under the Zone Names drop down list, select the zone“symmetry1”.

b. Set its Type as Deforming.

c. Select the Geometry Definition tab.

d. Specify the Definition as “plane”.

e. Specify Point on Plane as 0,0,0

f. Specify Plane Normal as 0,0,1

g. Click Create at bottom of dialog box to create this dynamic mesh zone.

The list of Dynamic Mesh Zones on the right side of the dialog box now includes the “sym-metry1”.

6. Define the dynamic mesh settings needed for the surface “symmetry2”, which is the second wall in thex-y plane. This surface will be affected by the solid body’s displacement, and its mesh needs to be ableto deform.

a. Under the Zone Names drop down list, select the zone “symmetry2”.

b. Set its Type as Deforming.

c. Select the Geometry Definition tab.

d. Specify the Definition as “plane”.

e. Specify Point on Plane as 0,0,0.4

f. Specify Plane Normal as 0,0,1

g. Click Create at bottom of dialog box to create this dynamic mesh zone.

The list of Dynamic Mesh Zones now includes the “symmetry2”.




7. Define the dynamic mesh settings needed for the surface “wall_bottom”, which is the two surfaces onthe bottom of the fluid zones (the two surfaces are interrupted by the solid body in the middle of thegeometry). This surface is not affected by the solid body’s displacement, and so its mesh should remainstationary.

a. Under the Zone Names drop down list, select the zone “wall_bottom”.

b. Set its Type as Stationary, then click Create at bottom of dialog box to create this dynamic meshzone.

The list of Dynamic Mesh Zones now includes the “wall_bottom”.

8. Repeat the previous step's instructions to create stationary dynamic mesh zones for the three surfacesbelow. These three surface complete the enclosed cavity, and they are not affected by the solid body’sdisplacement. Their mesh should remain stationary.

• “wall_top”

• “wall_side1”

• “wall_side2”

9. Define the dynamic mesh settings needed for the surfaces in the zone “wall_deforming”, which are thesurfaces surrounding the solid body. These surface will deform throughout the simulation.

a. Under the Zone Names drop down list, select the zone “wall_deforming”.

b. Set its Type as System Coupling, then click Create at bottom of dialog box to create this dynamicmesh zone.

The list of Dynamic Mesh Zones now includes the “wall_deforming”.

10. You now have seven dynamic mesh zones defined and listed on the right of the dialog box. Click Close.

Adding the Solution Settings

Set the solutions settings in the Fluent application so that your fluid system is ready to be solved:

1. On the left side of the Fluent application, select Solution > Solution Methods.

a. Under Pressure-Velocity Coupling > Scheme, select Coupled.

b. Under Spatial Discretization > Momentum, ensure Second Order Upwind is selected.

2. On the left side of the Fluent application, select Solution > Calculation Activities, then specify AutosaveEvery (Time Steps) to be 2.

3. On the left side of the Fluent application, select Solution > Run Calculation, then:

a. Specify Number of Time Steps to be 10. Note that the system coupling’s number of time steps willoverride this value.



b. Specify the Max Iterations/Time Step to be 5. This value is the maximum amount of times thatFluent can iterate within a coupling iteration.

c. Leave the default Time Step Size (s) as 1, but note that the system coupling’s time step size willoverride this value.

4. On the left side of the Fluent application, select Solution > Solution Initialization. Under InitializationMethods, ensure the Standard Initialization option is selected.

5. In Solution > Solution Initialization, click Initialize.


7. If you intend to execute a command line run using the setup from the Fluent system, go to Preparing fora Command-Line Run of the Fluent System (p. 97).

8. If you do not intend to execute a command line run using the setup from the Fluent system, Select File> Close Fluent to close Fluent and to return to the Project Schematic.

The setup for the Fluid system is complete. Remember that you will not solve the fluid analysisfrom the Fluent application because you are using the System Coupling system to solve bothstructural and fluid systems at the same time. In the next section, you will set up the SystemCoupling system.

Proceed to the section Defining and Running the Coupling in the System Coupling Applica-tion (p. 97).

Preparing for a Command-Line Run of the Fluent System

If you intend to execute a command line run using the set up from the Fluent system, select File >Export > Case from the main menu in the Fluent user interface, and specify the path and Case File(SystemCouplingOscillatingPlate_CmdLine\fluidFlow.cas) that you will use later.

Important

You should perform this step before updating the coupled solution within the Workbenchenvironment for the following reasons:

• Editing the Fluent system’s Setup cell after a solution is executed will clear all existing solutionfiles.

• Editing the Fluent system’s Solution cell after a solution is executed will load the most recent(rather than the original) case and data files.

You may now close Fluent.

Defining and Running the Coupling in the System Coupling Application

In the System Coupling system, you are setting up the coupling between your Structural and Fluidanalyses. You will use the System Coupling system to solve both of these analyses at the same time.

Notice that in the Structural and Fluid systems, all of the cells up to Setup are marked as up-to-date.




Setting the Basic Analysis Values

To set up the transient analysis settings for your coupled analysis:

1. In the Project Schematic, double-click the System Coupling system’s Setup cell (C2).

In the dialog box, click Yes to allow upstream data to be read. The System Coupling system is ob-taining data from the Structural and Fluid systems’ Setup cells (A5 and B4).

The System Coupling application opens in a new tab in your Workbench project.

2. In Outline of Schematic C1: System Coupling, select System Coupling > Setup > Analysis Settings.

3. In Properties of Analysis Settings (on the bottom left):

a. Set Duration Controls > End Time to 10.

The end time is the same as the Structural system’s time duration. The choice of 10 s givesenough time to observe the plate oscillating a few times. System Coupling’s end time valuealways overrides the number of time steps specified in the Fluent application.

b. Set Step Controls > Step Size to 0.1.

The coupling iteration size is same as the transient analysis’ time step, and the choice of 0.1s is small enough for use to observe the plate’s oscillations to a reasonable degree. SystemCoupling’s step size value always overrides the time steps size specified in the Fluent applica-tion.

c. Ensure the Maximum Iterations is set to 5.

For this system to converge, 5 coupling iterations within each coupling step is sufficient. Ifyour own system has trouble converging within the coupling step, you may want to increasethe number of maximum iterations or reduce the time step size.

Creating the Data Transfers

For your two-way coupled analysis, data from the Structural and Fluid solutions need to be sharedthroughout the solution process. System Coupling coordinates the transfer of data between these twosystems using the Data Transfers that you create.

1. In Outline of Schematic C1: System Coupling, expand System Coupling > Setup > Participants untilall region components are visible.

2. Ctrl-select the "wall_deforming" (from the Fluid system) and "Fluid Solid Interface" regions (from theStructural system). With both selected, right-click on one of those regions and select Create DataTransfer.

Under System Coupling > Setup > Data Transfers, Data Transfer and Data Transfer 2 are created:

a. Data Transfer:here, the surface of the Structural system around the plate transfers displacement tothe surface of the Fluid system around the plate.

b. Data Transfer 2: here, the surface of the Fluid system around the plate transfers force to the surfaceof the Structural system around the plate.



Click on System Coupling > Setup>Data Transfers > Data Transfer. In the Properties of Data-Transfer on the bottom left, notice that the source, target and variable transferred are alreadydefined for each of these data transfers. These settings are also already defined for Data Transfer2.

Preparing System Coupling for Restarts

You should ensure that System Coupling is producing restart data, in the event that the System Couplinganalysis needs to be restarted.

1. Under System Coupling > Setup > Execution Control, select Intermediate Restart Data Output. Therestart output frequency for the system coupling analysis is defined and controlled by these settings.

2. In Properties of Intermediate Restart Data Output:

• Set Output Frequency to At Step Interval.

• Set Step Interval to 5.

3. Select File > Save to save your settings before solving.

Note

Recall that earlier, the Fluent auto-save frequency was set to 2 so that Fluent will outputresult files (case and data files) every two time steps (that is, 2, 4, 6, 8, 10, etc.). Fluentwill also output additional result files at 5, 10, 15, 20 etc. based on the Step Intervalfrequency specified for the Intermediate Restart Data Output. In CFD-Post, both setsof files will be available for post-processing.

Solving and Restarting the Coupled Analysis

During the solution process, the System Coupling system coordinates the solving of your Structural andFluid systems as well as the data transfers between these two systems. The Fluid system solves usingthe Structural solution’s displacement data, and the Structural system solves using the Fluid solution’sforce data.

1. To start solving the coupled analysis, in Outline of Schematic C1: System Coupling, right-click Solutionand select Update.

The solution progress begins, and progress is summarized in the System Coupling Chart andSolution Information views, as well as the Workbench schematic progress view. This solution willrun for 100 coupling steps because you specified an end time of 10 s in System Coupling (“timeduration” in Mechanical), and each coupling step represents 0.1 s (“step size” in System Coupling,and “time step” in Mechanical).

Note that you can alternatively start solving the coupled analysis from Workbench’s ProjectSchematic:

a. To return to the Project Schematic, click on the Project tab in Workbench. To start the solutionprocess from the Project Schematic view, right-click the System Coupling system’s Solution cell(C3) and choose Update.




Notice that the Structural and Fluid systems’ Solution cells’ (A6 and B5) update operationsare disabled because the coupled solution process must be run through the System Couplingsystem.

b. Click on the System Coupling tab to return to the System Coupling system and observe the coupledsolution progress.

If you closed the System Coupling application and so there is no System Coupling tab, youcan re-open the System Coupling user interface by double-clicking on its Solution cell (C3).

2. On the bottom right of the screen, click on Show Progress to see the progress of your solution.

3. As your analysis is solved, in the Solution Information view, information from the System Coupling Logfile is displayed. Useful information includes:

a. Each coupling step and coupling iteration is recorded with information about convergence of thedata transfer.

b. At the beginning of the file (scroll up in your Solution Information view), there is an overview ofthe participants (the Fluid and Structural system), the data transfers, the System Coupling settings,and a mapping summary.

c. The Mapping Summary has information about the percentage of nodes on your fluid-structure inter-face that are mapped. This information is used to determine the quality of the mapping in your system.

4. Restart data will be output during the solution process. An additional note will be seen in the SystemCoupling log output under Solution Information indicating the name and frequency of the systemcoupling result file. For example, the intermediate result file is written: scResult_01_000005.scr. The restartdata for Fluent will also be output at the same frequency during the coupled solution. When the coupledsolution completes, Mechanical restart files (that is, file.r001, file.r002 etc.) will be visible in the Workbenchproject files (that is, they are automatically transferred from the solver temporary/scratch folder). The filenaming convention is such that file.r001 refers to a Mechanical restart file at step 5, file.r002 refers to aMechanical restart file at step 10, and so on.

5. The System Coupling solution is complete when the System Information view reads “System couplingrun completed successfully.”

6. Select File > Save to save the project, and then click on the Project tab to return to the Project Schem-atic.

Preparing for a Command-Line Run of the System Coupling System

If you intend to execute a command-line run using the setup from the System Coupling system, youneed to export the System Coupling Input (SCI) file. To do this:

1. In your Project Schematic, make sure that the System Coupling Setup cell (C2) is in an up-to-date state.

2. If your System Coupling tab is not open, double-click System Coupling’s Setup cell (C2).

3. From the System Coupling tab, in the main menu, select File > Export SCI File.

4. Specify the path and SCI file (SystemCouplingOscillatingPlate_CmdLine\coupling.sci)that you will use later.



5. Select File > Save to save the project, and then click on the Project tab to return to the Project Schem-atic.

Viewing Results in CFD-Post

You will use CFD-Post to view the results of your coupled analysis. You have simulated the plate oscil-lating in a closed cavity filled with air. The results you have obtained show the plate and surroundingair for a few oscillations, and you will be able to use CFD-Post to see the motion of the plate as it isdamped.

In Workbench, you need to set up the Project Schematic so that CFD-Post can read the solution ofyour Structural and Fluid systems.

To view the results in CFD-Post:

1. In the Project Schematic, drag the Structural Solution cell (A6) to the Fluid Results cell (B6).

2. Double-click the Fluent Results cell (B6) in the Fluid system to launch CFD-Post.

CFD-Post opens in a new window. Both sets of results are loaded into the CFD-Post session, andare ready for you to view.

Creating an Animation

An animation is a good way to view results in a transient analysis. In this animation, you will show:

• The pressure and velocity of the fluid on the symmetry plane

• The deformation of the plate geometry, with stress visible

Set up your animation:

1. From the task bar at the top of the CFD-Post application, select Tools > Timestep Selector to open theTimestep Selector dialog box.

The Timestep Selector dialog box shows the results time history for both Fluent and MAPDL systemcoupling.

2. In the Timestep Selector dialog box, on the Fluid tab, select a Time of 0.2 s for the Fluid case, then clickApply.

Close the Timestep Selector dialog box.

3. Under Cases > Fluid at 0.2s > Part Fluid, check the “symmetry1” zone under the Fluid case to displaythat zone, then double-click to edit it.

a. In Details of symmetry1, on the Color tab set the Mode to Variable and set Variable to Pressure.

b. On the Render tab, clear the Lighting check box and check Show Mesh Lines.

c. Click Apply to save your changes. The pressure at 0.2 s is now visible on the one side of the fluidgeometry.




4. Under Cases > Structural at 0.2s > Default Domain, check the Default Boundary zone, then double-click to edit it.

a. In the Details of Default Boundary, on the Color tab, set the Mode to Variable and set Variableto Von Mises Stress.

b. On the Render tab enable Show Mesh Lines.

c. Click Apply. Stress is now visible on the structural body.

5. From the task bar at the top of the CFD-Post application, select Insert > Vector to create a vector plot.Accept the default name and click OK.

a. In the Details view on the Geometry tab, set the Locations to symmetry1, set Sampling to FaceCenter, and ensure that Variable is set to Velocity.

b. On the Symbol tab, set Symbol to Arrowhead3D.

c. Click Apply. A vector plot of the velocity is now visible on the one side of the fluid geometry.

6. In the Outline under User Locations and Plots, clear the Default Legend View 1 check box.

7. From the task bar at the top of the CFD-Post application, select Insert > Text and click OK to accept thedefault name.

a. In the Details of Text 1 view, for Text String, type Time = . Check the Embed Auto Annotation,and from the Expression drop-down list select Time.

b. On the Location tab, set X Justification and Y Justification to None, and set the Position text as0.1 in the first field, and 0.2 in the second field.

c. Click Apply.

The corresponding transient results are loaded into the Animation in CFD-Post, and when you run theanimation, you can see the mesh move in both the Fluent and Mechanical regions.

1. Zoom in so that you can see the oscillating plate clearly.

2. At the top of the CFD-Post application, click Animation .

The Animation dialog box appears.

3. Select Keyframe Animation.

4. In the Animation dialog box:

a. Click New to create KeyframeNo1.

b. Highlight KeyframeNo1, then change # of Frames to 48.



c. Load the last timestep (100) using the Timestep Selector (found at the top of the CFD-Post Inter-face).

d. Back in the Animation dialog box, click New to create KeyframeNo2.

The # of Frames parameter has no effect for the last keyframe, so leave it at the default value.

e. Click the More Animation Options button , then check the Save Movie check box.

f. Click Browse next to Save Movie to set a path and file name for the movie file.

If the file path is not given, the file will be saved in the directory from which CFD-Post waslaunched.

g. Click Save.

The movie file name (including path) will be set, but the movie will not be created yet.

h. If frame 1 is not loaded (shown in the F: text box in the middle of the Animation dialog box), click

To Beginning to load it.

Wait for CFD-Post to finish loading the objects for this frame before proceeding.

i. Click Play the animation .

The movie will be created as the animation proceeds. This process will be slow, since a timestepmust be loaded and objects must be created for each frame.

j. Save the results by selecting File > Save Project from the main menu.

k. Close the animation dialog box. Your animation is now saved in the file path you specified. You canplay the video in any media player.

Plotting Results on the Solid

You will use a chart to display the deformation of the solid body. One point at the top of the plate isused to track the displacement in the chart. This chart is a useful way to view the damping that occursin the plate’s motion due to the interaction with the fluid.

1. Create a point in the solid domain by using node number 77. This point is at the top corner of the solidbody, and will be used to track the deformation of the plate.

a. From the task bar at the top of the CFD-Post application, select Insert > Location > Point. Click OKto accept the default name.

b. In the Details view, on the Geometry tab, set Domains to Default Domain, set Method to NodeNumber, and set Node Number to 77.

c. Click Apply. On your model, cross hairs appear on node number 77, so you can see where this pointis on your solid body.




2. To view the deformation using the point you just created, insert an XY Transient Chart for the data at thisnode (“Point 1”). In the chart you create, the x-axis is time, and the y-axis is the total mesh displacement.

a. From the task bar at the top of the CFD-Post application, select Insert > Chart; click OK to acceptthe default name.

b. In the Details view, on the General tab, set Type to XY - Transient or Sequence

c. On the Data Series tab, for Name type System Coupling, and set Location to Point 1.

d. On the X Axis tab, ensure that the Expression is Time.

e. On the Y Axis tab, set the Variable to Total Mesh Displacement X.

3. Click Apply to generate the chart of mesh displacement over time.

After the chart is generated, note the damping that is visible in the plate’s motion. The plate doesnot return to equilibrium in this chart because of the length of time we chose for the simulationof this case. To see the full damping of the system, you would need to simulate the case for alonger time duration.

4. Save the project and then select File > Close CFD-Post.

Post-Processing in Mechanical

You can also see the structural results of your FSI analysis in the Mechanical application. Note that theMechanical system does not have any information about results on the fluid bodies.

1. From the Project Schematic, double-click the Results cell (A7) to relaunch ANSYS Mechanical.

The Mechanical application opens in a new window.

2. In the Outline view, right-click Solution A6 and select Insert > Stress > Equivalent (von Mises) results.

3. Right-click Solution A6 again and select Insert > Deformation > Directional results.

4. Right-click Solution A6 again and select Evaluate All Results.

The equivalent stress and directional deformation of the place are now visible on your model.

5. Under Solution A6 click Equivalent Stress to view the stress on the structural body.

6. Under Solution A6 click Directional Deformation to view the deformation of the structural body.

7. From your Project Schematic, save the project.

All systems are now complete and the Project Schematic is up-to-date.

Setting Up and Executing a Coupled Analysis Restart from Workbench

1. In the Mechanical application,

a. Under Project > Model > Transient, select Analysis Settings.

b. In Analysis Settings Details, set Restart Type to Manual.



c. In Analysis Settings Details, set Current Restart Point to Load Step 50, Substep 1 (that is, 5s).

d. Close ANSYS Mechanical.

2. From the Project Schematic, double-click the Fluid Solution cell (B5):

a. From the File menu, select Solution Files....

b. In the Solutions Files dialog box that appears, click on 100 time steps, 10s - Current to deselect it,and then click on 50 time steps, 5s to select this time step.

c. Select the Read button. Fluent will read in the case/data file associated with 5s.

d. Close Fluent.

3. From the Project Schematic, double-click the System Coupling Setup cell (C2):

a. From the outline, select Setup > Analysis Settings.

b. In Properties of Analysis Settings, under Initialization Controls, from the Coupling Initializationdrop-down list, select Step 50, Time 5[s].

c. Optional: Under Execution Control > Intermediate Restart Data Output, set Output Frequency toNone. If this is not done, there will be a second set of restart files output under the Workbench project.

4. To start solving the coupled analysis restart, right-click the Solution branch in Outline of Schematic C1:System Coupling, and select Update. A summary of the solution progress in the System Coupling Chart(starting from 5s) and Solution Information views (also starting from 5s), as well as the WorkbenchSchematic Progress view.

5. Once your solution is complete, select File > Save to save your project.

6. You have now used the Workbench, Fluent, Mechanical, and System Coupling interfaces to complete thistutorial’s simulation. If you would like to complete the optional steps to run this tutorial using the commandline, continue with Executing the Coupled Analysis from the Command Line (p. 105).

Otherwise, you are now finished Oscillating Plate with Two-Way Fluid-Structure Interaction tutorial.When you are finished viewing your results, and select File > Save from the main menu, and thenFile > Exit to close your Workbench project.

Executing the Coupled Analysis from the Command Line

This section describes how to execute the analysis for this tutorial from the command line. In this example,all executables are run in batch mode (there are no user interfaces or launchers) from a standard install-ation on a single Windows 64-bit machine.

Note

In order to be able to execute runs from the command line, all executables and dynamiclibrary dependencies must be properly resolved. For more information, see Executing SystemCouplings Using the Command Line.




Preparing the Required Input Files

Runs executed from the command line require input files for each of the executables used in the coupledanalysis.

1. If you have not been creating the input files for the command-line analysis as you worked through thetutorial, then follow the instructions in Optional: Preparing for a Command-line Run (p. 82) to create thefile structure for the command-line run.

2. If you have not been creating the input files for the command-line analysis as you worked through thetutorial, then follow directions in the sections referenced below and create the listed input files in theSystemCouplingOscillatingPlate_CmdLine directory:

a. Create the file structural.dat according to Preparing for a Command-Line Run of the StructuralSystem (p. 90).

b. Create the file fluidFlow.cas according to Preparing for a Command-Line Run of the FluentSystem (p. 97).

c. Create the file coupling.sci according to Preparing for a Command-Line Run of the SystemCoupling System (p. 100).

3. An additional input file is required to execute the Fluent solver in batch mode. In the SystemCouplin-gOscillatingPlate_CmdLine directory, create a journal file named fluidFlow.jou that containsthe following:

file/start-transcript "Solution 1.trn"file set-batch-options , yes ,file/read-case/fluidFlow.cass i i(sc-solve)wcd FLUENTRestart.cas.gzexitok

Running the Analysis

To run the analysis:

1. Open a command window, and from the SystemCouplingOscillatingPlate_CmdLine\Coup-ling_CmdLine subdirectory, run System Coupling service using the following command:

"C:\Program Files\ANSYS Inc\v160\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe" –inputFile ..\coupling.sci

Tip

You may prefer to add the previous command to a batch file.

Now when you run the System Coupling service command, the coupling service starts and createsthe System Coupling Server File (SystemCouplingOscillatingPlate_CmdLine\Coup-ling_CmdLine\scServer.scs). For details, see Files Generated by Coupling Service (p. 56).

2. Open scServer.scs and review its contents, which will be similar to the following:



12345@yourmachine2SolutionStructuralSolution 1Fluid

where:

• 12345 is the server port

• yourmachine is the host's name

• 2 indicates that two participant connections are expected

• The unique names to be used when starting the structural and fluid flow solvers are, respectively:"Solution" and "Solution 1". The unique names from the solver(s) are encoded in the coupling serviceinput file and are reported here along with the names of the systems in the Workbench schematic.Note this correlation, since the unique names are needed when starting the respective solvers. Note,as well, that the unique names are determined by Workbench and can vary depending upon the orderin which systems were introduced into the schematic.

3. Copy the fluidFlow.cas file into the FluidFlow_CmdLine subdirectory.

This step ensures that Fluent treats that subdirectory as the run directory, and generates all sub-sequent case and data files there. By keeping the basic input files separate from the run directories,you can easily clear or delete the run directories for retries.

4. From a new command window, change to the FluidFlow_CmdLine subdirectory, then run the Fluentsolver by entering the following command:

"C:\Program Files\ANSYS Inc\v160\fluent\ntbin\win64\fluent.exe" 3ddp -hidden -driver null -scport=12345 -schost=yourmachine -scname="Solution 1" -i ..\fluidFlow.jou>FLUENT.out

5. From a new command window, change to the Structural_CmdLine subdirectory, then run theMechanical APDL solver by entering the following command:

"C:\Program Files\ANSYS Inc\v160\ansys\bin\winx64\ANSYS160.exe" -b -scport 12345-schost yourmachine -scname "Solution" -i ..\structural.dat -o ANSYS.out

Note

• In steps 4 and 5 above, you may need to adjust the coupling service port and host (12345and yourmachine, respectively) and solvers' unique names ("Solution" and "Solution 1"for the Mechanical APDL and Fluent solvers, respectively) based upon information extractedfrom the system coupling server file.

• The input file name,structural.dat, will need to be replaced with the name of themanually-created input file (e.g.mapdl.dat) if such a file was created to enable a resumefrom a Mechanical APDL database file.




Restart Analysis Execution

For the sake of simplicity, the restart analysis uses the same solver and coupling service directories inwhich the initial analysis was performed.

Preparing the Required Input Files

In the SystemCouplingOscillatingPlate_CmdLine directory, create the following:

1. Create a restart journal file for the Fluent solver. Name this file fluidFlowRestart.jou, and have itcontain the following:

file/start-transcript "Solution 2.trn" file set-batch-options , yes , rcd/fluidFlow-1-00050.cas(sc-solve) exit ok

Note

The "-1-" in the file name fluidFlow-1-00050.cas represents the run number andmay be different in your system, depending upon how many runs were completed beforewriting the .cas file.

2. Create a restart input file for the Mechanical APDL solver. Name this file structuralRestart.dat,and have it contain the following:

/batch/solu/gst,on,onantype,4,rest,50,1,continuesolvesavefinish/exit

Run the Analysis

Much as when you ran the initial analysis:

1. Open a command window, change to the Coupling_CmdLine subdirectory, and run the SystemCoupling service using the following command:

"C:\Program Files\ANSYS Inc\v160\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe" –inputFile ..\coupling.sci –resultFile scResult_01_000050.scr

2. Open the system coupling server file (scServer.scs) and note the coupling server’s port and host.Note that the solvers’ unique names have not changed because they are encoded in the coupling service’sinput file.

3. Change to the FluidFlow_CmdLine subdirectory, and run the Fluent solver by entering the followingcommand:

"C:\Program Files\ANSYS Inc\v160\fluent\ntbin\win64\fluent.exe" 3ddp -hidden -driver null -scport=12345 -schost=yourmachine -scname="Solution 1" -i ..\fluidFlowRestart.jou>FLUENTRestart.out



4. Change to the Structural_CmdLine subdirectory, and run the Mechanical APDL solver by enteringthe following command:

"C:\Program Files\ANSYS Inc\v160\ansys\bin\winx64\ANSYS160.exe" -b -scport 12345 -schost yourmachine -scname "Solution" -i ..\structuralRestart.dat -o ANSYSRestart.out

Note

In steps 3 and 4 listed above, you may need to adjust the coupling service port andhost (12345 and yourmachine, respectively) and solvers' unique names ("Solution"and "Solution 1" for the Mechanical APDL and Fluent solvers, respectively) based uponinformation extracted from the system coupling server file.

Loading the Results into CFD-Post

To load the Results files into CFD-Post:

1. To start CFD-Post, from the Start menu, go to Start > All Programs > ANSYS 16.0 > Fluid Dynamics >CFD-Post 16.0.

2. From CFD-Post, select File > Load Results.

3. Open the final CAS file, which will have a name similar to FluidFlow_CmdLine\fluidFlow-1-00100.cas.

4. Again select File > Load Results.

5. In the dialog box that appears, select Keep current cases loaded, and clear Open in new view.

6. Open the file Structural_CmdLine\file.rst. When post-processing results, your structural resultsare named after the name of the file they are loaded from. From this command line run, your structuralresults will appear under the name “file” (because of file.rst).

7. Proceed to Viewing Results in CFD-Post (p. 101) for instructions on how to post-process the results. Whenfollowing these instructions, remember that your command line structural results will appear under thename ”file”, and not “Structural”.





Tutorial: Heat Transfer from a Heating Coil

In this tutorial you will learn about executing a sequence of one-way thermal transfers in a heat exchangerusing the System Coupling infrastructure.

DetailsFeatureComponent

Steady State ThermalAnalysis SystemsANSYS Workbench

Fluid Flow (Fluent)

System CouplingComponent Systems

External Data

ImportGeometry and Named SelectionsDesignModeler

Defining the physicsSteady State Thermal

Defining the physicsANSYS Fluent

Defining the couplingSystem Coupling

Compare film coefficientsCase ComparisonCFD-Post

Examine temperatures andtemperature distributions

This tutorial includes:Overview of the Problem to SolvePart 1:Transferring Data from the Steady-State Thermal Analysis to the Fluid Flow AnalysisPart 2:Transferring Data from the Fluid Flow Analysis to the Steady-State Thermal Analysis

Overview of the Problem to Solve

In this tutorial, a variety of ANSYS Workbench systems are used to analyze conjugate heat transfer in asimple heat exchanger.

The heat exchanger involves the coupling of solid and fluid models. The solid model consists of a copperalloy heating coil and the fluid model consists of an annular region with flowing water that envelops

the coil. A constant heat generation source of 8.72 e+6 W/m3 is specified for the coil and the heatgenerated is made to convect away from its surface by water flowing at a nominal speed of 0.4m/s.



The tutorial is divided into two parts. In the first part, the convective heat transfer experienced by theheating coil is estimated and the steady-state thermal analysis is executed for the solid model. Theresulting temperature from the coil surface is then used to execute the fluid analysis. In the second partof the tutorial, the thermal analysis for the solid model is also executed, however the convective heattransfer obtained from the fluid analysis is used instead of the original estimate.

In a case such as the one described here, there are advantages to using one-way data transfer insteadof conjugate heat transfer or two-way analysis. One-way data transfer works well when separate groupsare performing the computational fluid dynamics analysis and the thermal finite element analysis. Theindividual solutions are simpler with a one-way analysis than they would be with a two-way coupledanalysis. Another advantage of one-way data transfer is that it provides a more flexible workflow; anythermal variable of interest can be transferred. Coordinate transformations can also be applied whenusing one-way data transfer.

Part 1: Transferring Data from the Steady-State Thermal Analysis to theFluid Flow Analysis

This part of the analysis has the following steps:Creating the ProjectAdding Analysis and Component SystemsAdding New Materials for the ProjectAdding Geometry to the ProjectPreparing the Steady-State Thermal Source DataUsing External Data to Access the Steady-State Thermal Source DataPreparing the Fluid Flow AnalysisPreparing and Executing the Coupled Thermal AnalysisReviewing Results in CFD-Post


1. Start ANSYS Workbench:

• To launch ANSYS Workbench on Windows, click the Start menu, then select Start > All Programs >ANSYS 16.0 > Workbench 16.0.



• To launch ANSYS Workbench on Linux, open a command line interface and enter the path to runwb2.For example:

~/ansys_inc/v160/Framework/bin/Linux64/runwb2

The Project Schematic appears with an Unsaved Project. By default, ANSYS Workbench is configuredto show the Getting Started dialog box that describes basic operations in ANSYS Workbench. Tocontrol the display of this dialog box, select Tools>Options from the main menu and go to ProjectManagement>Startup and select or clear the Show Getting Started Dialog check box.

2. Create a directory where you will store your project (this is your working directory). For example, underMy Documents, create a directory named SystemCouplingHeatingCoilTutorial.

3. Select File>Save.

A Save As dialog box appears.

4. Select the path to your working directory to store files created during this tutorial.

5. Under File name, type SystemCouplingHeatingCoil and click Save.

The project files and their associated directory locations appear under the Files view. To make theFiles view visible, select View>Files from the main menu of ANSYS Workbench.

6. This tutorial uses the geometry file,HeatingCoil.agdb, and a Fluent mesh file,HeatingCoilFLU-ENTMesh.msh, for setting up the project. To access tutorials and their input files on the ANSYS CustomerPortal, go to http://support.ansys.com/training.

Copy the supplied geometry file, HeatingCoil.agdb, and the mesh file, HeatingCoilFLU-ENTMesh.msh, to the user_files directory that is in the SystemCouplingHeating-Coil_files directory.

By working with copies of the geometry and mesh files in your working directory, you preventaccidental changes to the original files.

Setting the Units in ANSYS Workbench

To ensure that the units for this project are set correctly, select Units from the top menu bar and confirmthat Metric (kg,m,s,°C,A,N,V) is checked.

Adding Analysis and Component Systems

In ANSYS Workbench, set up an analysis system in order to transfer data from a Steady-State Thermalsystem to a Fluid Flow system, as outlined in this section.

1. Drag a Steady-State Thermal system from the Analysis Systems toolbox and drop it onto the ProjectSchematic.

2. From the Analysis Systems toolbox, drag a Fluid Flow (Fluent) system onto the Project Schematic anddrop it to the right of the Steady-State Thermal system.

3. You will use the System Coupling infrastructure to obtain data from the Steady-State Thermal systemfor use in the Fluid Flow (Fluent) system. From the Component Systems toolbox, drag a SystemCoupling system and drop it to the right of the Fluid Flow (Fluent) system.



Part 1:Transferring Data from the Steady-State Thermal Analysis to the Fluid FlowAnalysis

http://support.ansys.com/training

4. Drag the Setup cell from the Fluid Flow (Fluent) system (B4) and drop it onto the Setup cell in the SystemCoupling system (C2). That establishes the relationship between the fluid flow and the external data thatis coming in through system coupling.

5. From the Component Systems toolbox, drag an External Data system onto the Project Schematic anddrop it between the Steady-State Thermal system and the Fluid Flow (Fluent) system.

Note that this changes the lettering of the Fluid Flow (Fluent) system from (B) to (C) and theSystem Coupling system from (C) to (D).

6. Drag the Setup cell from the External Data system (B2) and drop it onto the Setup cell in the SystemCoupling system (D2).

7. Save the project: click Save .

The Project Schematic should appear as shown in Figure 14: Project Schematic of a Fluid Solid Interface,System Coupling Problem (p. 114).

Figure 14: Project Schematic of a Fluid Solid Interface, System Coupling Problem

The Structural and Fluid systems contain various cells. ANSYS Workbench provides visual indications ofthe state of a cell at any given time via icons on the right side of each cell. In Figure 14: ProjectSchematic of a Fluid Solid Interface, System Coupling Problem (p. 114), most cells appear with a blue

question mark , indicating that cells need to be set up before continuing the analysis. As these cellsare set up, the data transfer occurs from top to bottom. See Understanding Cell States for a descriptionof various cell states.

Now the project is ready for further processing. A project schematic such as this with interconnectedsystems enables you to perform a multiphysics analysis by adding a new geometry, setting up thephysics of the individual systems (Steady-State Thermal, and Fluid Flow systems in this example), andalso viewing the results.

Adding New Materials for the Project

1. On the Project Schematic, double-click the Engineering Data cell in the Steady-State Thermal system(A2).

In the tab that appears, you will set the Material Properties for the coil.

2. In the Outline of Schematic A2: Engineering Data window, note that Structural Steel is the first entryin the Material section. Right-click the empty row at the bottom of the Material section, just below theStructural Steel entry to add a new material for the project.



3. Select Engineering Data Sources.

4. In the Data Source column of the Engineering Data Sources tab, select General Materials.

5. In the Outline of General Materials section, click the plus sign beside the Copper Alloy option to addcopper alloy material to the project.

6. You now have all the material properties that you need for the project. At the top of your Workbenchwindow, close the Engineering Data tab to return to the Project Schematic.

7. From the main menu, select File>Save to save material settings to the project.


Add the geometry by importing an existing DesignModeler file.

1. On the Project Schematic, right-click the Geometry cell in the Steady-State Thermal system (A3) andselect Import Geometry>Browse.

2. In the Open dialog box, browse to your working directory, select SystemCouplingHeating-Coil_files>user_files>HeatingCoil.agdb, and click Open.

Preparing the Steady-State Thermal Source Data

You will now define the physics for the steady-state thermal analysis.

Assigning the Material to the Geometry

To assign the material to the geometry:

1. On the Project Schematic, double-click the Model cell in the Steady-State Thermal system (A4). This willopen the Mechanical application.

2. In the Mechanical application, right-click Project>Model (A4)>Geometry>Part>Container and selectSuppress Body.

3. Click Project>Model (B4)>Geometry>Part>Coil.

4. In the Details of “Coil” view, use the Material>Assignment drop-down box to select Copper Alloy.

Generating the Mesh

Define and generate a mesh for the structural model of the heating coil.

1. In the Mechanical application Outline view, right-click Project>Model (A4)>Mesh and select Insert>Meth-od.

2. In the viewer window, select the whole coil geometry in the viewer window by clicking on it.

3. In the Details of “Automatic Method” - Method view, click Scope>Geometry>Apply.

4. In the Details of “Automatic Method” - Method view, select Definition>Method>Sweep.

5. Click the box to the right of Definition>Free Face Mesh Type. Select All Tri.




This creates triangular elements on the source face. These triangular elements then get sweptthrough the coil body during the Sweep. Quad elements are not used for this case because thecoarse mesh that is used would result in a poor quality mesh on the source face.

6. Click Project>Model (A4)>Mesh to open the Details of “Mesh” view.

7. In the Details of “Mesh” view, select Sizing>Element Size and enter 0.05.

8. Right-click Project>Model (A4)>Mesh and select Generate Mesh.

Defining the Physics for the Structural Analysis

Define the physics for the steady-state thermal portion of the problem.

Defining the Steady-State Thermal Analysis

1. Define the initial temperature:

1. In the Mechanical application Outline view, click Project>Model (A4)>Steady-State Thermal(A5)>Initial Temperature.

2. In the Details of “Initial Temperature” view, change Definition>Initial Temperature Value to250°C.

2. Define the internal heat generation:

1. Right-click Project>Model (A4)>Steady-State Thermal (A5) and select Insert>Internal HeatGeneration.

2. Select the coil body in the viewer window.

3. In the Details of “Internal Heat Generation” view, click Geometry>Apply.

4. In the Details of “Internal Heat Generation” view, change Definition>Magnitude to 8.72e6

W/m3. This is the source for the steady-state thermal calculation.

3. Define the convection boundary condition to allow the heat to escape from the area around the coil:

1. In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal(A5) and select Insert>Convection.

Convection values will reflect the heat removal from the coil surface.

2. In the Details of “Convection” view, change Scope>Scoping Method to Named Selection.

3. In the Named Selection drop-down box, select CoilSurface.

4. Change Definition>Film Coefficient to 1000 W/m2·°C.

5. Change Definition>Ambient Temperature to 30°C.

The convection boundary condition is applied to the outer coil surface, not to the ends. Theheat that was introduced in the previous step will be dissipated due to convection.



The heat transfer (film) coefficient value should be approximately 1000 W/m2·°C. This will bethe estimate that you use for this part of the tutorial. In a later part of this tutorial, you willrun the CFD analysis and compare the estimated number to the calculated number for theheat transfer coefficient value. At that time, you will replace the estimated heat transfer coef-ficient value with the full set of heat transfer coefficient values that are calculated from thefluid dynamics side.

4. Define the fluid-solid interface:

1. In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal(A5) and select Insert>Fluid Solid Interface.

2. In the Details of “Fluid Solid Interface” view, change Scope>Scoping Method to Named Selection.

3. In the Named Selection drop-down box, select CoilSurface.

4. In the Export Results drop-down box, select Yes. This setting will make Mechanical export the staticresults to an ANSYS External Data file (the .axdt file).

The .axdt files are generated from the results on defined fluid solid interfaces. These fileswill be used to transfer thermal data from ANSYS Mechanical to ANSYS Fluent when you areusing External Data and System Coupling (this is the method used in this tutorial).

5. Add the temperature and total heat flux results to review:

1. In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal(A5)>Solution (A6) and select Insert>Thermal>Temperature.

2. In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal(A5)>Solution (A6) and select Insert>Thermal>Total Heat Flux.

6. Click File>Save Project.

Executing the Structural Analysis

To create the temperature and heat flux distribution solutions, click the Solve button from themain toolbar at the top of the Mechanical application.

Post-Processing the Structural Analysis Results

When the solution is complete, review the temperature and total heat flux distribution results.

1. To look at the temperature distribution, in the Mechanical application Outline view, click Project>Model(A4)>Steady-State Thermal (A5)>Solution (A6)>Temperature.




Figure 15: Temperature of the Coil

2. To look at the total heat flux distribution, in the Mechanical application Outline view, click Project>Model(A4)>Steady-State Thermal (A5)>Solution (A6)>Total Heat Flux.



Figure 16: Total Heat Flux Distribution on the Coil

In the Messages view, just under the viewer window, there will be an Info message that states,"The thermal results at the Fluid Solid Interface(s) have been written to the solver files directory."This tells you that the .axdt file has been created. You now have an ANSYS External Data file(.axdt file) that can be brought into External Data. This file contains the Temperature and HeatFlow values exported from the Fluid Solid Interface region that you defined. You will import thisfile into External Data to provide thermal boundary conditions for Fluent via the System Couplingcomponent.

3. Click File>Save Project and File>Close Mechanical.

Using External Data to Access the Steady-State Thermal Source Data

You can access the ANSYS External Data file (.axdt file) as follows:

1. In the Files window, scroll down to find the .axdt file, and note that it’s named fsin_1.axdt.

2. On the Project Schematic, double-click the Setup cell in the External Data system (B2).

3. Under Location in the Outline of Schematic section, click the button and select Browse. Browse tothe fsin_1.axdt file.

4. Select the fsin_1.axdt file and click Open.




All the information about the external data for this project has been automatically entered intothe appropriate data sections. In the Properties of File section, the format type is AXDT. The Tableof File section summarizes the x, y and z coordinate data that appear in the Preview of File section.There are also temperature values in Celsius and heat rate in Watts that have been imported fromthe fsin_1.axdt file. You can scan this data to ensure that it seems reasonable for this project.

5. Close the External Data tab to return to the Project Schematic.

6. On the Project Schematic, right-click the Setup cell in the External Data system (B2) and select Update.

Preparing the Fluid Flow Analysis

To prepare the fluid flow analysis, import the fluid mesh, and set up the physics in Fluent.

Importing the Mesh for the Fluid Flow Analysis

Import an existing Fluent mesh file into the fluid analysis.

1. In the ANSYS Workbench Project Schematic, right-click the Mesh cell in the Fluid Flow (Fluent) system(C3) and click Import Mesh File>Browse.

2. Browse to your working directory, select SystemCouplingHeatingCoil_files>user_files>HeatingCoilFLUENTMesh.msh, and click Open.

In the Fluid Flow (Fluent) system, notice that the Geometry cell is automatically deleted and theMesh cell is renamed to Imported Mesh.

Defining the Physics for the Fluid Flow Analysis

Define the physics for the fluid analysis.

1. In the Fluid Flow (Fluent) system (C3), double-click the Setup cell to start Fluent.

2. In the Fluent Launcher, select Double Precision. Click OK.

The mesh file is automatically loaded into the Fluent session.

3. Right-click Setup>Models>Energy (Off) and select Edit. Check the Energy Equation check box and clickOK.

4. Right-click Setup>Models>Viscous (Laminar) and select Edit. For the Model, select k-epsilon (2 eqn).For the Near-Wall Treatment, select Scalable Wall Functions. Click OK.

5. Change the fluid material to water:

1. Right-click Setup>Materials>Fluid and select New....

2. Click the Fluent Database button.

3. In the Fluent Fluid Materials section, select water-liquid (h2o<l>).

4. Click the Copy button to add water as the material and click Close.

5. In the Create/Edit Materials panel, click Change/Create and Close.



6. Select Setup>Cell Zone Conditions, then select Edit.

7. In the Fluid dialog box, change Material Name to water-liquid. Click OK.

6. Set the boundary conditions, starting with the fluid-solid interface on the coil’s surface:

1. Select Setup>Boundary Conditions.

2. Before you select a zone, select the Highlight Zone check box in order to display only the selectedzone in the viewer.

3. Under Zone, select coilsurface, and then select the Edit button.

4. In the Wall dialog box, one the Thermal tab, set the Thermal Conditions to via System Coupling.Click OK.

This boundary is now marked as one that will participate in couplings. It will be able to accepteither temperature or heat flow data.

7. Set the inflow boundary:

1. Under Zone, select inflow.

2. Change the Type to velocity-inlet and click Yes to accept this change.

3. In the Velocity Inlet dialog box, set the Velocity Magnitude to 0.4 and click OK.

8. Set the outflow boundary:

1. Under Zone, select outflow.

2. Change the Type to pressure-outlet and click Yes to accept this change.

3. In the Pressure Outlet panel, verify that the Gauge Pressure is 0. Click OK.

9. Set up the solution controls:

1. Select Solution>Solution Methods and set the Scheme to Coupled.

2. Select Solution>Monitors>Residual, and right-click to select Edit.

3. In the Residuals Monitors panel, under Equations, change Absolute Criteria for energy residualfrom 1e-06 to 1e-05.

4. Click OK.

In this problem, energy residuals level off around 8e-06. This step ensures that Fluent terminatesonce this level of convergence is reached during the coupled analysis.

5. Select Solution>Run Calculation and set the Number of Iterations to 200.

10. Select File>Save Project to pass the changes to Workbench.




11. Now that the physics is defined, close Fluent.

The next step is to set up the coupled thermal analysis.

Preparing and Executing the Coupled Thermal Analysis

1. Set up the data transfer in the system coupling system:

1. In the ANSYS Workbench Project Schematic, double-click the Setup cell in the System Couplingsystem (D2).

2. Click Yes in the pop-up window to read the upstream data.

3. In Outline of Schematic D1: System Coupling, select System Coupling>Setup>Participants>External Data>Regions>File1.

This file is the .axdt file that was copied into External Data in the Using External Data toAccess the Steady-State Thermal Source Data (p. 119) section.

4. In Properties of Region: File1, right-click Topology>Output>File1:Temperature1 and select CreateData Transfer.

5. In Outline of Schematic D1: System Coupling section, select System Coupling>Setup>DataTransfers>Data Transfer.

6. In Properties of Data Transfer : Data Transfer section, in Target>Participant, select Fluid Flow(Fluent).

7. In Target>Region, select coilsurface.

8. In Target>Variable, select temperature.

9. Select File>Save.

Note

For one-way steady thermal coupled analyses, it is good practice to use one couplingiteration per run. This can be done by selecting Analysis Settings in the tree viewand changing Maximum Iterations to 1 in the details view. However, in this tutorial,default settings will be used.

2. Add Fluent’s solution monitor:

1. Click on the Project tab in Workbench to return to the Project Schematic, keeping the SystemCoupling tab open.

2. From the Project Schematic, right-click the Fluid Flow (Fluent) system’s Solution cell (C4) and selectProperties. In the Properties view that appears in Workbench, ensure that Solution Monitoring ischecked. This setting will allow you to monitor Fluent’s solution from Workbench.



3. Right-click the Fluid Flow (Fluent) system’s Solution cell (C4) and select Show Solution Monitoring.A new tab opens with the solution monitor. When you solve your analysis using System Coupling,use this tab to watch Fluent solve the fluid part of this analysis.

3. Solve the coupled analysis and add a new chart to monitor the solution:

1. Click on the System Coupling tab in Workbench to return to the system coupling interface.

2. In Outline of Schematic D1: System Coupling, right-click System Coupling>Solution and selectUpdate.

This starts the coupled analysis. Fluent connects up to the coupling service and will run end-to-end. Fluent will accept external data and will run through its full convergence. A summaryof the solution progress is in the System Coupling Chart and Solution Information views.

3. In Outline of Schematic D1: System Coupling, right-click System Coupling>Solution>ChartMonitors and select Create Chart to create a new system coupling chart.

4. Right-click the new Chart 2 that appears and select Add Variable>External Data>Data Trans-fer>Value>Average.

5. Right-click the Chart 2 again and select Add Variable>Fluid Flow (Fluent)>Data Transfer>Value>Av-erage.

This new chart shows the difference between the average nodal temperature values in Kelvin,transferred from the source region to the target region. Notice that the source and targetvalues differ by approximately 11 degrees. This difference is due to mismatching of the nodeson the source and target sides.

4. Close the System Coupling tab to return to the Project Schematic.

Reviewing Results in CFD-Post

Review the graphical results of the project in CFD-Post.

1. In the ANSYS Workbench Project Schematic, double-click the Results cell in the Fluid Flow (Fluent) system(C5) to start CFD-Post.

2. View the temperature along the ZX plane:

1. From the CFD-Post toolbar, click and select Plane.

2. Click OK to accept the default name of Plane 1.

3. In the Details of Plane 1 section, in the Geometry tab, set the Method to ZX Plane.

4. In the Color tab, set the Mode to Variable and the Variable to Temperature.

5. Set the Range to User Specified, the Min to 300 K, and the Max to 305 K.

The full temperature range is much larger due to temperature extremes on a small fractionof the surface. By neglecting those extreme temperatures, more colors are used over the rangeof interest.




6. Click Apply.

7. For a better view, click the y axis on the Viewer triad.

Figure 17: Advection of Heated Water Out of the Heat Exchanger (p. 124) shows the thermalboundary layer around the coil surface and illustrates how the warmed-up fluid is being ad-vected out of the heat exchanger.

Figure 17: Advection of Heated Water Out of the Heat Exchanger

3. View the heat transfer coefficient on the coil’s surface:

1. Disable the plane view by deselecting the Outline>User Locations and Plots>Plane1 check box.

2. Select the Outline>Cases>FFF>part container>coilsurface check box.

3. Right-click the coil surface in the Viewer and select Color>Wall Heat Transfer Coefficient.

Earlier in the tutorial, the heat transfer (film) coefficient value was estimated at approximately

1000 W/m2·°C. This estimate is slightly lower than with the average calculated value on thecoil surface in Figure 18: Wall Heat Transfer Coefficient on the Coil Surface (p. 125).

Note that there is variability in the distribution of the heat transfer coefficient on the coil surface.In the second part of this tutorial where you will replace the estimated heat transfer coefficient



value with the full set of heat transfer coefficient values that are calculated from the fluid dy-namics side. The data calculated here will be exported from CFD-Post and brought into asystem coupling analysis of a steady state thermal system.

Figure 18: Wall Heat Transfer Coefficient on the Coil Surface

4. View the wall adjacent temperature on the coil’s surface:

• Right-click the coil surface in the Viewer and select Color>Wall Adjacent Temperature.

In the Defining the Steady-State Thermal Analysis (p. 116) section, we estimated that the ambienttemperature of the coil surface would be approximately 30°C. Figure 19: Wall Adjacent Tem-perature on the Coil Surface (p. 126) shows that the calculated wall adjacent temperature isclose to this value with some variation. In the second part of this tutorial, you will replace theestimated ambient temperature with the full set of adjacent temperature values that are cal-culated from the fluid dynamics side. The data calculated here will be exported from CFD-Postand brought into a system coupling analysis of a steady state thermal system.




Figure 19: Wall Adjacent Temperature on the Coil Surface

Part 2:Transferring Data from the Fluid Flow Analysis to the Steady-StateThermal Analysis

This part of the analysis has the following steps:Exporting the DataAdding Additional Analysis and Component SystemsUsing External Data to Access the Fluid Flow Source DataPreparing the Steady-State Thermal AnalysisPreparing and Executing the Coupled Thermal AnalysisReviewing Results in the Mechanical Application

Exporting the Data

Export results from the first part of the tutorial.

1. If you are not already in CFD-Post, in the ANSYS Workbench Project Schematic, double-click the Resultscell in the Fluid Flow (Fluent) system (C5) to start CFD-Post.

2. Click File>Export>Export External Data File.

3. In the Export External Data File panel, confirm that the File path is pointing to user_files/export.axdt.



4. For the Location, select coilsurface.

5. In the Select Recommended Variables box, select HTC and Wall Adjacent Temperature.

6. Click Save and close CFD-Post.

Adding Additional Analysis and Component Systems

The physics for this steady-state thermal system is identical to the physics in the first part of this tutorial,except that the data for the convection boundary condition will be obtained from the output from thefirst part of this tutorial through system coupling.

1. In order to create a copy of the first system, right-click the Setup cell (A5) in the Steady-State Thermalsystem and select Duplicate. The setup for this duplicate system (E) is identical to the setup of the ASteady-State Thermal system. Duplicating from the Setup cell in this way produces a new system withshared Engineering Data, Geometry and Model. The existing Setup cell state is copied to the new system.

2. From the Component Systems toolbox, drag a System Coupling system and drop it to the right of theCopy of Steady-State Thermal system.

3. Drag the Setup cell from the Copy of Steady-State Thermal system (E5) and drop it onto the Setup cellin the System Coupling system (F2).

4. From the Component Systems toolbox, drag an External Data system onto the Project Schematic anddrop it to the left of the Copy of Steady-State Thermal system. This External Data system will providedata to the Steady-State Thermal system through the System Coupling system.

Note that adding this system changes the lettering of the Copy of Steady-State Thermal systemfrom (E) to (F) and the System Coupling system from (F) to (G).

5. Drag the Setup cell from the External Data system (E2) and drop it onto the Setup cell in the SystemCoupling system (G2).

Figure 20: Project Schematic of a Fluid Solid Interface, System Coupling Problem Part 2



Part 2:Transferring Data from the Fluid Flow Analysis to the Steady-State ThermalAnalysis

Using External Data to Access the Fluid Flow Source Data

The fluid flow source data was generated in the fluid analysis in the first part of this tutorial. Providethe path to this data so that it can be used in the analysis.

1. In the Project Schematic, double-click the Setup cell in the second External Data system (E2).

2. In the Outline of Schematic section, under the Location column, click the ellipsis button and selectBrowse. Browse to the file named export.axdt that was exported from CFD-Post. Click Open.

3. Close the External Data tab to return to the Project Schematic.

4. In the Project Schematic, right-click the Setup cell in the External Data system (E2) and select Update.

Preparing the Steady-State Thermal Analysis

Remove the estimated convection value from the thermal analysis.

1. Double-click the Setup cell in the Copy of Steady-State Thermal system (F5).

2. In the Outline view of the Mechanical application, under Project>Model (A4, F4)>Steady-State Thermal2 (F5), the estimate for the Convection condition is present. Remove this estimate by right-clickingConvection and selecting Delete.

3. The Fluid Solid Interface condition does not need to be modified.

In the first part of this tutorial, the fluid solid interface was used so that an .axdt file was createdand temperature values and heat rates from that fluid solid interface region were output. In thesecond part of this tutorial, the Fluid Solid Interface will be used to receive data from systemcoupling as well as to create an .axdt file.

4. Close the Mechanical application.

5. Right-click the Setup cell in the Copy of Steady-State Thermal system (F5) and select Update.

Preparing and Executing the Coupled Thermal Analysis

Set up the data transfer and solve the coupled analysis.

1. Double-click the Setup cell in the System Coupling system (G2). Click Yes to read the upstream data.

2. In the Outline of Schematic G1: System Coupling window, Ctrl-select Fluid Solid Interface and File 1.Right-click File 1 and select Create Data Transfer to automatically create a pair of data transfers.

Data Transfer created transfers the heat transfer coefficient, and Data Transfer 2 created transfersthe reference temperature.


4. Right-click the Solution section and select Update. As the system solves, system coupling draws the datafrom the external data system and provides it to the Mechanical application.

5. After the solution has finished, close the System Coupling tab to return to the Project Schematic.

6. Right-click the Results cell in the Copy of Steady-State Thermal system (F7) and select Update.



Reviewing Results in the Mechanical Application

1. Double-click the Results cell in the Copy of Steady-State Thermal system (F7) to open the Mechanicalapplication.

2. To compare the results from the first part of the tutorial with those from the second part, split the viewerwindow into two parts. Click the Viewport icon in the top menu bar and select Vertical Viewports.

3. Click in the left viewport and then in the Outline view, click Steady-State Thermal (A5)>Solution(A6)>Temperature.

4. Click in the right viewport and then in the Outline view, click Steady-State Thermal 2 (F5)>Solution(F6)>Temperature.

The left view now shows the original, uncoupled case and the right view is the coupled result.

5. To synchronize the two views, click the Manage Views icon in the top menu bar.

6. The Manage Views window appears in the lower left part of the Mechanical application window. Click

in the left viewport and click the Create a View icon, .

7. Click in the right viewport, select View 1 and click the Apply a View icon, .

8. To allow a better comparison of the two sets of results, both the scales should be changed to the samevalues. Double-click the second-lowest value in the colored legend and change it to 200 and change thesecond-highest value in the colored legend to 1600. Do this in both the left and right viewports.




Figure 21: Comparison of Coil Temperature Contours from the First and Second Parts of theTutorial

As noted at the end of the first part of the tutorial, the constant heat transfer coefficient value appliedin the thermal analysis of the coil under-predicts the spatially-varying values generated by the fluidanalysis. Qualitative and quantitative differences are consequently observed between thermal analysesof the coil in the first and second parts of the tutorial. When the larger, spatially-varying heat transfercoefficient values are applied, the resulting temperature values decrease appropriately and temperaturevariations occur over the coil surface. For example, the lowest temperatures are observed on the lower,side portions of the coil cross-section due to increased convective cooling in those regions. Convectivecooling decreases on the lower and upper portions due to flow stagnation and recirculation, respectively.The effect of the larger, spatially-varying heat transfer coefficient values on the heat flux solution valuesfrom the thermal analyses corroborate these observations.

1. To compare the total heat flux, select the left viewport and click Steady-State Thermal (A5)>Solution(A6)>Total Heat Flux.

2. Select the right viewport and select Steady-State Thermal 2 (F5)>Solution (F6)>Total Heat Flux.



Figure 22: Comparison of Coil Total Heat Flux Contours from the First and Second Parts ofthe Tutorial

3. When you are finished viewing your results, select File>Save Project from the main menu, and thenFile>Close Mechanical. Select File>Exit to close your Workbench project.





IndexAanalysis settings, 9

best practices, 12Analysis Settings field, 9Analysis Type property, 9

Bbest practices, 73

Cchart monitors, 29CHT (Conjugate Heat Transfer) example, 111co-simulation participant

controlled by the system coupling service, 1co-simulation participant sequencing, 76co-simulation participant stability, 76

ramping, 76solution stabilization, 76

command line options, 34command line usage, 33conjugate heat transfer

example, 111coupled analyses

debugging using graphical monitor output, 75debugging using text based monitor output, 74restarting, 35

coupled solution execution timeusing sequencing to reduce, 77

coupling initialization, 10coupling service

files used by, 55

DData Transfers

creating, 14data transfers, 16, 44

algorithms, 46profile preserving, 47

conservative profile preserving, 47interpolation algorithms, 52mapping algorithms, 46

bucket surface, 48General Grid Interface (GGI), 51

postprocessing interpolated data, 53ramping, 53under-relaxation, 54

pre-processing algorithms, 45Debug Output control, 20debugging two-way coupled analyses, 73

using graphical monitor output, 75using text based monitor output, 74

duration controls, 10Duration Defined By property, 10

EEnd Time, 10examples

CHT, 111conjugate heat transfer, 111heat exchanger, 111solid region, 111steady state simulation, 111transient mechanical analysis, 88

Ffluid-solid interactions, 79

Ggeneral analysis type, 12

Hheat exchanger example, 111

Iinitialization controls, 10input file, 58

Llog file, 20

scLog.scl, 64

Mmaximum iteration, 11minimum iteration, 11

OOutline view, 8output

intermediate, 22output frequency

all steps, 23at step interval, 23none, 22

Pparticipant

exchanges data in a coupled analysis, 1summary, 13

performanceimproving in system coupling, 77



Properties view, 8

Rramping, 53region

part of the topology of a coupling participant, 13restart data

intermediate, 22restart points, 10results file

scResults_##_######.scr, 57

SScene view, 9sequencing of solution steps, 20sequential solutions, 20server file

scServer.scs, 56service input file

scInput.sci, 55service log file

scLog.scl_, 57service overview, 41service shutdown file

scStop.stop, 55simulation example

steady state, 111simultaneous solutions, 20solid

region example, 111Solution Information view, 9solvers

coupling two-model interactions, 80steady state simulation example, 111Step Controls property, 11step size, 11structural deformations

modeling, 79structural properties

assigning the material to geometry, 87system coupling

analyze decoupled systems first, 73context menus

Setup cell, 23Solution cell, 32

overview, 1workspace, 7

system coupling management, 41convergence management, 43evaluating convergence, 43inter-process communication, 41process synchronization, 41

system coupling statesSetup cell, 23Solution cell, 32

Ttransient analysis type, 13transient mechanical analysis

example, 88

Uunder-relaxation, 54

Vview

convergence plots, 9outline, 8properties, 8scene, 9solution information, 9


Index