Learning Forum

[bxddstl]

Professor, ,I am a novice. I have a qusetion .

I want to do a simulation of fluent , but the mesh occured an error , and I don't know which part occured the error,so how can i check which part of fluent 3d geomoetry occurs the error , because it is hard to find the error part in the text log to see the test.(I mean in ansys mechaniacl i can use the " identify element violations "to mark the error body in the 3d model rather than in the text log so i can find it clearly. I want to know whether there are the samilar function like " identify element violations " in ansys fluent)

Thank you for your help.?

[RK]

Hello,
To get more clarity in your question, is it related to Fluent Meshing or the solver? Also, what is the error that you get?

[bxddstl]

Here are the error messages:

(DP 0) Update-Dynamic-Mesh failed. Negative cell volume detected.
(DP 0) Error when making a remote call to participant Solution 12.Please do not save the project if you would like to recover to the last saved state.
(DP 0) The maximum contact stiffness is too big. This may affect the accuracy of the results. You may need to scale the force unit in the model.
(DP 0) An unknown error occurred during solution.Check the Solver Output on the Solution Information object for possible causes.
(DP 0) A solver failure occurred during the run in the Transient Structural system


Update failed for the Solution component in System Coupling.The coupled update for system Transient Structural threw an exception. Error updating cell Solution in system Transient Structural.

So i think maybe it is because of the dynamic mesh have some wrong.

The error always tell me what is wrong ,but i do not which part of the body occur the error,andit is hard for me to find the wrongamong all the bodys and all the settings(especially in Coupling system).

Can you tell me how to deal with the error messages? Not just this message ,i want to know the the process of dealing with all error messages in FSI.
Thank you.

[Stephen Orlando]

Hi,
The first message is important, there is a negative volume in the Fluent mesh. You'll need to adjust your Dynamic Mesh settings to avoid this. Also, here are my general System Coupling FSI recommendations.

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. For CFX, 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)