Sesam user coursehome.hib.no/ansatte/tct/ftp/H2017 Marinteknisk Analyse...20 February 2017 HydroD Global Analysis Wadam SAFER, SMARTER, GREENER SOFTWARE 20 February 2017 DNV GL HydroD

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HydroD Global Analysis Wadam20 February 2017 SAFER, SMARTER, GREENERDNV GL © 2014

Ungraded

SOFTWARE

20 February 2017DNV GL

HydroD Global Analysis Wadam

Sesam user course

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DNV GL © 2014

Ungraded

HydroD Global Analysis Wadam20 February 20172

Scope of presentation

Describe commands needed for performing a global analysis of a panel model, and their folders– Environment modelling– Analysis models– Roll damping– Sectional loads– Loading conditions– Offbody points– Execution directives

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Wave Modeling

It’s a Wave – Body Interaction problem Regular Waves in Wadam

– Wind generated gravity Waves– Linear (Airy) Wave Theory– Monochromatic (1st Order) and Bi-chromatic (2nd order)– Unidirectional

Input of Sea State information for:– Stochastic Linearization of:

– Drag loads on Morison members– Roll Damping

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Definition of waves – Wadam

Incoming wave defined as

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X

YA Wave amplitude

Wave number =

Angular frequency =

Wave direction (“going to” direction)

Input to Wadam:Wave direction +

Wave length or Wave period or Angular frequency

))sincos(cos(),,( kykxtAtyx

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Environment folder

Locations, (one ore more objects)– Depth, density, gravity– Referring to frequencies, directions,

spectrum etc., defined in Directions and Water (hydrodynamic analysis)

Air– Wind profiles (hydrostatic analysis)

Directions– Direction set, directions

(hydrodynamic analysis) Water

– Frequency set, spectrum, current, wave spreading etc. (hydrodynamic analysis)

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Directions folder

Define wave propagating angles Direction

– Specification of one single direction

– Used when specifying the main direction in a sea state to combine with wave spreading

– Used to specify direction of current

Direction Set– Define a list of directions– Used in frequency domain

analysis

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Water folder

Contains– wave spectrums– spreading functions– current profiles– frequency sets– phase sets– wave height functions – regular wave sets (Wasim)

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Locations

A location is a complete description of all environmental data necessary to compute the environmental loads on your structure or vessel This includes

– Directions for wave and current– Wave, current and depth data– Sea state data

– used for stochastic linearization & roll damping in Wadam

– Irregular time conditions – used in time domain analysis in Wasim

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Frequency domain condition

Created by right-clicking on a location object

Combines a set of M frequencies with a set of N directions, i.e. loads will be calculated for M×N waves.

NOTE: The wave amplitude is not relevant for a Wadam analysis (only for Wasim)

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Sea State

Used in drag linearization and stochastic roll damping Contains data required to

produce an irregular seaWave spectrum, spreading, sea

state duration A spectrum is used from the

given start heading and up to the next start heading

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Restoring matrix

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General Damping

The damping can be frequency independent or not by selecting Interpolate

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Critical Damping

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Critical damping and natural period

The equation

ξ ξξ 0

will have harmonic solutions only when

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The natural period is approximately

2

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Display of strip model

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The Roll damping model is valid for monohull ships with XZ symmetry only

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Quadratic Roll damping

For stochastic linearization a quadratic coefficient can also be used – Roll for both Wadam and Wasim– Pitch for Wasim only

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Offbody points

Points Grid or From File– Animation in Xtract

Specified– Postprocessing in Postresp

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Compartment effects – Options in Mass model setup

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Creating a Wadam run

Select a Single body or Multi-body analysis

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Run dialog: Models to be used in run

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Selecting condition implicitly also selects location

Reset dialog to default settings

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Run dialog: Execution directives

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Select if data check only

Acceptance criteria for static balance

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Run dialog: Execution directives - Drag

Additional definitions needed in Execution directives for drag linearization

– Constant drag velocity (used for all waves)

– Stochastic linearization– Wave height linearization

Define convergence criteria (similar to roll damping calculations)

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Run dialog: Drift Forces & Solver

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Expensive

Cheap

If number of panels is larger than maximum matrix size (default = 5000) the direct solver is replaced by a block-iterative solver.→ Use direct solver if sufficient RAM (Increase the number)

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Run dialog: Roll damping

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Automatic iteration for short term statistics

Start values in iteration process if stochastic iteration (strip model)

Roll damping strip model is valid for ships only

Option for quadratic roll damping

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Run dialog: Print switch

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This controls the amount of print in the print file from Wadam, WADAM1.LIS

For most cases use Normal print.When using a roll damping model, the Model data switch may be useful.

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Run dialog: Result Files – Global Response

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Normally not changed, use default values.

For second order analysis only(Separate license required)

The Motion reference point may be user specified

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Run dialog: Advanced

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Restart files from different models can be stored using different file names

Normally not changed

Note the option for calculation of the mass model in HydroD (default) or Wadam

Automatic meshing of waterplane (not recommended)

Wave/current interaction

Normally not used

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Run dialog: Output directory (optional)

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Output files can be directed to a different directory than the run directory, e.g. the directory of a Sesam Manager project.

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Execute Wadam

Start from the Activity Monitor May include both Stability analyses and

Wasim analyses

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Possible to execute multiple activities (Threads) in parallel

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Execute Wadam – File handling (1)

HydroD will create new folders in the workspace directory Typical folder names are:

– conv_files (offbody surface file)– save_restart (wadam.rsq)– tmp_files– WadamRun1 (analysis files)– WadamRun2– etc.

HydroD will copy the selected T#.FEM files from the specified location into the workspace.The original files will not be moved Workspace files: <name>.hyd, <name>.sat Journal/log file: <name>.js

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Execute Wadam – File handling (2)

The analysis Wadam folder, e.g. WadamRun2 (default) will contain all the files for one Wadam run Model interface files: T#.FEM Print files (should be checked)

– WADAM1.LIS– poten.log– force.log

Results files– Global response: G1.SIF– Load files: L#.FEM, S#.FEM– Actual panel model: panelT1.FEM

.bak files and WSAV.SIN may be deleted

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Multibody Wadam analysis

The WadamRun dialog contains a Multi-body option to be selected

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Documents

Sesam user coursehome.hib.no/ansatte/tct/ftp/H2017 Marinteknisk Analyse...20 February 2017 HydroD Global Analysis Wadam SAFER, SMARTER, GREENER SOFTWARE 20 February 2017 DNV GL HydroD