Run FSI
The OptiStruct and AcuSolve runs can be run either in serial or parallel mode.
As explained in the previous sections, you simply initiate an OptiStruct or AcuSolve run and then start the second subsequent run. OptiStruct and AcuSolve will communicate via the specified port and exchange the required information with each other.
OptiStruct and AcuSolve may be run in parallel on distributed memory clusters. Both MPI and OpenMP parallelization modes are currently supported. For more information, refer to High Performance Computing.
- If the structural interface surface contains beam elements, no other elements can be used to define the damp surface. In other words, beam elements cannot be mixed with other elements to define the damp surface.
- A constant fixed time step should exist between the two solvers.
Activity Timeline | OptiStruct | AcuSolve |
---|---|---|
FSI Initiation | Set up standalone OptiStruct model co-located with the fluid domain | Set up standalone AcuSolve model co-located with the structural domain |
Standalone verification | Run independently on OptiStruct to verify model integrity | Run independently on AcuSolve to verify model integrity |
Identifying the interface | Identify the structural damp interface that is in contact with the fluid domain as a SURF entry or an element SET | Identify the fluid interface that is in contact with the structural domain as an element set |
Referencing the interface | Set up FSI Bulk Data Entry and reference the interface on the SURFID or ELSET fields | Set up EXTERNAL_CODE_SURFACE command
block and reference the interface elements using the
element_set parameter |
Modeling interface behavior | The USETAG field on the FSI Bulk Data Entry can be used to tag damp surfaces | The EXTERNAL_CODE_SURFACE command
block can be used to define parameters to model interface behavior
like velocity_type ,
mesh_displacement_type ,
temperature_type , and so on. For additional
information, refer to the corresponding solution page
(SFSI/TFSI). |
Activating FSI | The FSI Subcase Information Entry can be used to reference the FSI Bulk Data Entry | The external_code parameter is set
to on in the EQUATION command
block to activate the use of an external solver (OptiStruct) to provide the solution
field. |
Identifying communication protocols | The PORT and WAITTIME fields on the FSI Bulk Data Entry are used to identify the socket and the time OptiStruct waits for AcuSolve. | The EXTERNAL_CODE command block is
used to identify the socket and machine for communication. The
external_code_wait_time parameter can be
defined in the Acusim.cnf file to define the time
AcuSolve waits for OptiStruct. |
Specify run control parameters | The FCNVTOL,
DCNVTOL, TCNVTOL, and
FXCNVTOL fields on the FSI
Bulk Data Entry can be used to adjust exchange convergence
tolerances. The MINEX and MAXEX fields control the minimum and maximum number of exchanges per time step. The INITTS field identifies the initial AcuSolve time increment to start the coupling with OptiStruct |
The convergence_tolerance parameter
in the AUTO_SOLUTION_STRATEGY command block can be
used to determine the stagger convergence tolerances.The
There are additional sections of the AcuSolve run where the minimum and maximum number of exchanges are defined. |
Running FSI | Run the OptiStruct input file (with FSI data) and look for the cci.txt file in the working directory | After starting the OptiStruct run, initiate the AcuSolve run before the specified wait time.
If the runs are proceeding as expected, you should see
exchange/stagger information printed to:
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Note:
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FSI output | An .h3d file is generated with the structural results at the end of the simulation | The AcuSolve .log file is available to post-process the results of the simulation and can be loaded into HyperView. |
Note: Currently, the structural and fluid TFSI results
can be overlaid; however, the SFSI results can only be
post-processed separately.
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