discontinuity and overlap of elements in 2D thermoelasticity problem using quadratic elements

[Anup Basak]

Hello all,

I have solved a 2D mechanics (thermoelasticity) problem based on step 44 using quadratic elements (FE_Q). When I plot the solution in the deformed configuration (attached herewith) I see that at one place discontinuity gets developed between two elements (Fig. in page 2) and at some other place two elements overlap (Fig. in page 3). I have shown the locations in the figure of page 1.  However, when linear elements are used, this problem does not appear. In both the cases I get sufficient convergence.  I have confirmed this issue with both Visit and Paraview. I never encountered such strange problem while solving 3D problems. Hence it might be an issue related to post-processing.

Has anyone encountered such problem in the past? I shall be thankful if someone could tell me what might go wrong.

Thanks and regards,

Anup.

[Jean-Paul Pelteret]

Dear Anup,

Its possible that this is related to this issue. Do you perhaps have a minimal test case that reproduces the problem?

Best,

Jean-Paul

[Anup Basak]

Dear Jean-Paul,

Thank you very much for your reply.
Please find the sample code that reproduce the problem. The discontinuity and overlap can be seen by zooming into the mid-bottom and mid-upper part of the deformed configuration.

Thanks,
Anup.

[Jean-Paul Pelteret]

Dear Anup,

Thank you for your test case. I forgot to update this thread, but I was in fact able to reproduce the problem over the weekend. The problem appears to be in the interaction between the MappingQEulerian and DataOut classes. In the mean time you can work around it by not passing the Eulerian map to DataOut but rather transforming the body in the postprocessor itself (e.g. using Paraview's warp tool).

Regards,

Jean-Paul

[Anup Basak]

Dear Jean-Paul,

Yes, I have already checked it with Paraview's warp tool and it works correctly.

Thanks again,

Anup.

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