Elastic Waves, Time Explicit error

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Hello,

I am very new to COMSOL (and modelling in general) and I encountered an error while trying to model a very simple 2D steel block with a prespribed velocity on the top. The error I am getting is the following:

Undefined value found in discontinuous Galerkin formulation. -Geometry:geom1 -Domain:1 -Expression:comp1.elte.Gamma11

What I would like to see is the evolution of the velocity through the material. I have looked around but I cannot find what Gamma11 means or how to solve this issue. I would appreciate if anyone could help me.

Regards


1 Reply Last Post Dec 9, 2021, 4:52 a.m. EST
Kirill Shaposhnikov COMSOL Employee

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Posted: 5 months ago Dec 9, 2021, 4:52 a.m. EST
Updated: 5 months ago Dec 9, 2021, 4:59 a.m. EST

Hi Sofia,

It is a typical error message one can encounter when modelling with time-explicit DG-FEM interfaces, and, I have to admit, it is not very informative. The reason for the undefined value is usually due to the exponential growth of the solution, which, in its turn, can happen when the time-explicit integrations scheme becomes unstable: a mismatch between the time step and some mesh element, which leads to violating the CFL-condition.

It is hard to say what triggers the exponential growth of the solution without seeing your model. Therefore, I recommend that you submit a support case for your issue and tell the support representative to assign your case to me.

Best regards
Kirill

Hi Sofia, It is a typical error message one can encounter when modelling with time-explicit DG-FEM interfaces, and, I have to admit, it is not very informative. The reason for the undefined value is usually due to the exponential growth of the solution, which, in its turn, can happen when the time-explicit integrations scheme becomes unstable: a mismatch between the time step and some mesh element, which leads to violating the CFL-condition. It is hard to say what triggers the exponential growth of the solution without seeing your model. Therefore, I recommend that you submit a support case for your issue and tell the support representative to assign your case to me. Best regards Kirill

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