© 2005 ANSYS, Inc. 28 November 2005 ANSYS, Inc. Proprietary L1-1 CFX-10 Introduction Lecture 1

© 2005 ANSYS, Inc.28 November 2005

ANSYS, Inc. ProprietaryL1-1

CFX-10 IntroductionCFX-10 Introduction

Lecture 1

© 2005 ANSYS, Inc. L1-2

28 November 2005

ANSYS, Inc. Proprietary

Main Steps in CFD Analysis

Geometry

Physics Definition

Solver

Post-processing

CFX-10 IntroductionCFX-10 Introduction

Meshing

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Step 1: Geometry DesignModeler or Import from CAD create a solid representing the fluid flow region

Step 2: Meshing CFX-Mesh, CFX-TurboGrid or ICEM create a volume mesh using the solid

Step 3: Physics Definition CFX-Pre define physical models, material properties and boundary conditions

Step 4: Solver CFX-Solver Manager solve equations and produce a solution

Step 5: Post-processing CFX-Post analyze and visualize the solver results

Main Steps in CFD AnalysisMain Steps in CFD Analysis



Step 1: GeometryStep 1: Geometry

DesignModeler or CAD

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Create or Import the geometry

GeometryGeometry

Domain in which the governing equations will be solved and solution obtained

ANSYS DesignModeler can be used to create geometry

Results in one or more bodies

Not required if the mesh is imported from a separate application



Step 2: MeshingStep 2: Meshing

CFX-Mesh, ICEM or CFX-TurboGrid

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Mesh Generation Process of generating finite

volumes or elements CFX can accept meshes with

elements that are hexahedral, tetrahedral, prismatic (wedges), pyramids or any combination

Surface mesh and volume mesh make up the mesh

Meshes can be created in a different session or imported from another meshing utility

MeshingMeshing



Step 3: Physics DefinitionStep 3: Physics Definition

CFX-Pre

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The mesh defines the fluid domain(s) to be solved

Mesh Tab imports and manages grids Each imported mesh is stored as a Mesh

Assembly

Import Mesh into CFX-PreImport Mesh into CFX-Pre

Import Mesh

View Mesh Statistics for Selected Regions

Transform Mesh Assembly

Delete Mesh Assembly

Edit Render Options for Selected Regions

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Create ToolbarCreate Toolbar

To define your simulation, follow the toolbar from left to right

Some items are optional, depending on your simulation

Hold the mouse over each icon to see what it does

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In the simplest cases, the following items are required after importing the mesh

1. Domains

2. Boundary Conditions

3. Solver Control

4. Write Solve File

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Create a Coordinate Frame – if the default coordinate frame is not sufficient

Define the Simulation Type – steady state (default) or transient

Create a Domain – define properties of fluid, solid and/or porous domain(s)

Create a Subdomain – if you need to apply sources within a domain

Create a Source Point – if you need to apply a point source within a domain

Create a Boundary Condition – define what’s happening at the boundaries

Create a Domain Interface – for periodicity and to connect multiple domains

Define the Global Initial Conditions – initial conditions for all domains

Define the Mesh Adaption Criteria – to adapt the mesh as the solution progresses

Define the Solver Control Criteria – the parameters that control the Solver

Output Control and Monitor Points – the files the Solver outputs

Write Solver File – write a file and proceed to the Solver

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DomainsDomains

Define the regions in which the equations are solved

Fluid, solid and porous regions Pick the fluid(s) or solid materials Select the physical models:

Turbulence and Heat Transfer model Buoyancy Multiphase models Combustion and Radiation models Particle Tracking ……

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Boundary Conditions are needed to completely specify (or close) the problem

Required on all external surfaces of geometry Boundary values can be constants or CEL

expressions A Default Boundary Condition is applied to external

surfaces which have not been explicitly defined created automatically for each domain

All mesh regions are available in CFX-Post, not just Boundary Conditions

Boundary ConditionsBoundary Conditions

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There are 5 general types of boundary conditions INLET: allow flow into the domain only OUTLET: allow flow out of the domain only OPENING: allow flow in and out of the domain WALL: no flow, normal velocity is zero SYMMETRY: flat surface specifying plane of

symmetry

Boundary ConditionsBoundary Conditions

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Control of the CFX-5 Solver is undertaken by the use of Solver Parameters, set on the Solver Control form Convergence Control

> maximum number of iterations> timescale selection

Advection Scheme Convergence criteria

> MAX or RMS residual> conservation target

Solver ControlSolver Control

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CFX-Pre writes out a “Definition” (.def) file to run in the Solver Contains everything needed (mesh and physics)

to run the simulation. CFX-Pre stores mesh data in the “Geometry,

Topology and Mesh” (.gtm) file and physics in the .cfx file Keep these files to re-open simulations in CFX-

Pre

Write Solver FileWrite Solver File



Step 4: SolverStep 4: Solver

CFX-Solver Manager

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SolverSolver

Solve the governing equations Set the flow solver options Iteratively solve the governing

equations as a batch process Obtain convergence

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The Solver Manager is primarily used to: start a new calculation, or set up multiple runs restart a calculation from an earlier solution examine the problem information set up parallel runs monitor residuals, global balances, monitor

points, expressions, etc.

Solver ManagerSolver Manager



Step 5: Post-processingStep 5: Post-processing

CFX-Post

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CFX-PostCFX-Post

Examine results, either in graphical or numerical format

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Provides capability to quantify and visualize results

Typical Post functionality involves creating Locator Objects (Points, Lines, Slice

Planes, etc.) plotting Visualization Objects (Contours, Vectors,

etc.) on locators evaluating expressions on locators exporting data for further external analysis

CFX-Post also includes turbomachinery specific post-processing tools

CFX-PostCFX-Post

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CFX-Post: VisualizationCFX-Post: Visualization

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Main File Types in CFXMain File Types in CFX

CFX-Pre

CFX-Solver

CFX-Post

CFX-Pre case (.cfx) & GTM (.gtm) fileCFX Results File (.res)CFX Definition File (.def)Other mesh files

CFX Definition File (.def)

CFX Results File (.res)

CFX-Pre case (.cfx) & GTM (.gtm) file

CFX Definition File (.def)CFX GTM File (.gtm)

CFX Solver Output file (.out)

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Practical SessionsPractical Sessions

Practical 1: Duct Bend A simple example to take you through the

stages of setting up and running a model and then visualising the results

Practical 2: Duct Bend With Vanes Include heat transfer and turning vanes (thin

surfaces) in the above example.

Documents

© 2005 ANSYS, Inc. 28 November 2005 ANSYS, Inc. Proprietary L1-1 CFX-10 Introduction Lecture 1