Learning Forum

[Sanda]

[Stephen Orlando]

When running System Coupling and it stops running, the first thing to do is examine the output files for each solver to look for clues to what happened. For Fluent, look at the transcript .trn file. For Mechanical, look at the .out file. Also, look at the System Coupling log file, .scl. You can also try re-running the case and stopping it just before the timestep when it crashes, then examine the mesh in Fluent or CFD-Post to get more clues.
I recommend going over this tutorial in the Ansys documentation that shows a 2-way FSI simulation with Fluent and Mechanical. https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v202/en/sysc_tut/sysc_tut_oscplate_wb_fluent.html
System Coupling Tutorials \\ Tutorials with Workbench-Setup Workflows \\ Tutorials with Workbench Setup and Execution \\ Oscillating Plate FSI with Fluent and Mechanical
You can also look at the following for a similar tutorial but run with the System Coupling GUI outside of Workbench. The new System Coupling GUI (run outside of Workbench) is available by searching for "System Coupling 2019R3 (or newer)" in the Windows Start menu. https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/sysc_tut/sysc_tut_reedvalve_fluent.html
FSI simulations with very soft materials or membranes are prone to numerical instabilities. In 2020R1 we have introduced a stabilization method in System Coupling called the Quasi-Newton Stabilization Algorithm. Note that this has to be used with the new System Coupling GUI or Command Line Interface that is run outside of Workbench. More information here: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/sysc_ug/sysc_gen_scservice_dt_supplemental_iqnils.html
System Coupling User's Guide \\ System Coupling Data Transfers \\ Supplemental Processing Algorithms \\ Quasi-Newton Stabilization Algorithm
It is very important to build up the FSI simulation in stages as opposed to setting up the 2-way FSI right at the start. This document "Best Practices for Coupled Fluid-Structure Interaction (FSI)" describes this process and is available here: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/sysc_ug/sysc_bestpractices_fsi.html
System Coupling User's Guide \\ Best Practices for System Coupling \\ Best Practices for Coupled Fluid-Structure Interaction (FSI)

Steve