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Error: Undefined value found in discontinuous Galerkin formulation

Posted 10 ago 2023, 15:40 GMT-4 2 Replies

Chenxi Xu
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I got the error below:

Error: Undefined value found in discontinuous Galerkin formulation. -Geometry:geom1 -Boundaries:6-10, 15 -Expression:comp1.asbte1.g_aco_p

My model has multiphysics of acoustic-structural interface, and it's calculated in time domain, pysics included pressure acoustics and elacstic waves.

Could someone tell me what the possible reason causing this error? Or how can I access the expression mentioned in the error?

Thank you in advance.

2 Replies Last Post 11 ago 2023, 17:38 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 1 year ago 11 ago 2023, 15:34 GMT-4

Hi Chenxi,

I recently encountered similar problems in such a setup. The model was running fine in a rather ugly mesh and showed a similar error in a better and finer mesh. According to COMSOL support a reason may be inappropriate tuning of mesh size and time stepping. The time stepping adjustment is very critical in the time explicit solvers. So time stepping and meshing may be the field to play in. So far I didn't solve the issue and I am still working with the ugly mesh with locally bad aspect ratio. However this shows different issues at long runtimes.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Chenxi, I recently encountered similar problems in such a setup. The model was running fine in a rather ugly mesh and showed a similar error in a better and finer mesh. According to COMSOL support a reason may be inappropriate tuning of mesh size and time stepping. The time stepping adjustment is very critical in the time explicit solvers. So time stepping and meshing may be the field to play in. So far I didn't solve the issue and I am still working with the ugly mesh with locally bad aspect ratio. However this shows different issues at long runtimes. Cheers Edgar
Chenxi Xu
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Posted: 1 year ago 11 ago 2023, 17:38 GMT-4

Hi Edgar,

Yes, I also noticed that the model somehow works when I set the time range small, as I increase the time range while keeping the same time stepping, the error starts to show up. I may try to play with the mesh and see how things will work.

Thank you for your reply! I really apreciate it :))

Best, Chenxi

Hi Edgar, Yes, I also noticed that the model somehow works when I set the time range small, as I increase the time range while keeping the same time stepping, the error starts to show up. I may try to play with the mesh and see how things will work. Thank you for your reply! I really apreciate it :)) Best, Chenxi

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