Problem & some Background

We observed a mismatch between results of the perpendicual flap case when preparing this publication. In the end we used the Deal.II - SU2 and FEniCS - SU2 cases in the publication. They show good agreement. CalculiX - SU2 disagrees with these cases. Our current explanation for this behavior is that the CalculiX case uses C3D8 elements, which should not be used according to the CalculiX documentation (see "...the locking phenomena observed in the C3D8 element...").

Solution

From my current point we should therefore use the "right" elements for CalculiX (no idea which elements are the right ones). Note that this will also require modifications of the calculix-adapter, since up to my knowledge currently only C3D8 and C3D8R elements work (please correct me, if I'm wrong).

Additional Material

For debugging this case we developed a fluid-fake solver that I would like to share in this issue (see fluid-fake.zip). This allows to replace the fluid solver with a simple constant force for quicker debugging. I'm plotting the tip displacement over time. Already this simple setup can be used to show the mismatch of CalculiX and the other two solvers:

Code Versions

• tutorials: a166efadfe7dbd3231e14897dcbeecebb90ea97e
• fenicsprecice: v1.0.1
• precice: v2.2.0
• pyprecice: v2.2.0.1
• calculix-adapter: 4635aa87439d154269d7f6141e8684a733f3e68f
• dealii-adapter: f9c2c65eead05ecea1c2f7a1c7ff48fe5942f930
• dealii: v9.2.0
• calculix: did not check this, but I think it should be 2.16