Thanks for adding this!
Could you please add a README describing the case?
Please also check the conventions here: https://precice.org/community-contribute-to-precice.html#contributing-tutorials

All changes added.

This pull request has been mentioned on preCICE Forum on Discourse. There might be relevant details there:

https://precice.discourse.group/t/can-i-use-precice-to-simulate-a-droplet-impacting-on-an-elastic-substrate/1372/2

This pull request has been mentioned on preCICE Forum on Discourse. There might be relevant details there:

https://precice.discourse.group/t/question-about-using-overset-mesh-in-fsi-two-way-coupling/1446/4

This pull request has been mentioned on preCICE Forum on Discourse. There might be relevant details there:

https://precice.discourse.group/t/mppicfoam-precice/1783/2

Ready for re-review @MakisH

• Updated to preCICE v3
• Removed the 3D case. Will open a separate draft PR (beyond this distribution)
• Changed the setup to have "z" in span-wise direction. This way, we can use 2D as preCICE mesh dimensions. To this end, I copied the perpendicular flap meshes for both solvers.
• I then had to increase the stiffness of the flap to make the case work.

Please:

• Double-check, fix, or clean the OpenFOAM input files. Not much that I changed here.
• Sanity-check on conventions

@uekerman I went ahead and fixed most of the trivial issues. Still open:

• The simulation diverges for me. With your setup and the updated gravity, it diverges at 0.79. I tried making the flap stiffer, the fluid time step size smaller, but I could not achieve anything better, and it looks like we need a better solution.
• This case currently is set up using two meshes, relying only on pointDisplacement in the OpenFOAM style (old-style tutorials). I will try merging to a single mesh, maybe this already helps.
• We are using a fixed time step size for the flow simulation, which is generally a no-go for two-phase simulations. I don't know if subcycling works correctly, but it does not help (breaks earlier, the moment the water touches the pillar).

I switched the case to use one mesh, and this already helped a lot. The simulation now crashes later, at 0.945:

Maybe it is something with the outlet condition now.

By setting the upperWall to zeroGradient, the simulation completes (due to the max-time-windows) at 1.0.

With the current setup, the simulation final crashes at 1.435:

I assume we are losing mass somewhere, so maybe we need to check the boundary conditions again. Maybe the zeroGradient for the alpha.water was not such a smart choice in the end.

For context, if I use the same solid-calculix as with the perpendicular-flap, then the simulation crashes now at 0.79 with an abnormally deformed flap (shape change).

My last state 9b97b92 does indeed crash, but only at t=1.485.
CalculiX adapter: precice/calculix-adapter@ffeda14 (same as you)
OpenFOAM: OpenFOAM-2212
OpenFOAM adapter: precice/openfoam-adapter@b6e860ae79a35

For context, if I use the same solid-calculix as with the perpendicular-flap, then the simulation crashes now at 0.79 with an abnormally deformed flap (shape change).

That setup is indeed not stiff enough (i.e. the forces here are too high). (The fluid here is different from the one there)

Latest state here 27d3fd7 crashes at t=1.24.

With the old alpha.water (reverting a9cdff1), it crashes at t=0.91.

With a reduced water column height (1/2 height instead of 3/4 height) and a reduced timestep size (2e-3), I can run until t=5. Probably still sensitive, but good enough in my opinion.