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Cirion0000 July 6, 2009 14:26

Properly using symmetry with both CFX and ANSYS workbench for a FSI analysis, help!
DISREGARD THIS TOPIC. I solved it! (Mods feel free to lock/delete or whatever)

Allright, it was a pretty basic user error. I didn't have the structural section in the same quadrant as the fluid part (doh). Works now.

[EDIT] I was using the wrong material so it wasn't displacing much, and this is why the answer didn't make sense. Now however, with the correct material, I'm getting this error:

"Solver pivot warnings have been encountered during the solution. This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues. Check results carefully.
The unconverged solution (identified as Substep 999999) is output for analysis debug purposes. Results at this time should not be used for any other purpose.
The solver engine was unable to converge on a solution for the nonlinear problem as constrained. Please see the Troubleshooting section of the Help System for more information."

This error doesn't make sense, because it's the exact same material I used in a previous analysis before using symmetry...



I am trying to do an FSI problem using both ANSYS and CFX coupled together. I can do it, but the only problem is that as we all know 3-d solutions can get pretty nasty pretty quick with lots of iterations. So, I thought I'd try my luck with symmetry since my device is axisymmetric.

It seems that both ANSYS Workbench allows you to make the solid (structural) solution into a symmetric solution - and that CFX-pre lets you do a symmetric solution for the fluid as well. Now here's the problem. I can get the fluid part to do a symmetric solution, just fine, with no problems. I cut it into four pieces, and it works out well for me. But when I try to do the same for the solid part, it doesn't work properly. I get a solution convergance, but it doesn't make sense compared to what I'm getting without the symmetry on the structural part. Can you not do symmetry for both the fluid and structure part, or am I just doing it wrong?

Here's my solution methodology for the structural symmetry:

1. Load workbench (duh)
2. Start project, and import the primary structural geometry.
3. Tools > symmetry, # of planes (2), XY/XZ planes (cuts it into one fourth, it clearly works, at least in the Design Modeler part)
4. Start simulation based on this
5. Input the important loads (pressure, fixed support, FSI boundary) set up time intervals, etc...
6. Write input file, run the solver.
7. Get a solution (or not...)

Did I just miss a glaringly obvious step? I also tried putting in the symmetry regions in the simulation as well but it didn't seem to do anything.

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