Compare and document accuracy of results in partitioned heat conduction (OpenFOAM vs FEniCS)

[MakisH]

Originally posted by @BenjaminRodenberg in #406 (review)

I guess there was already an error/inaccuracy (compared to the FEniCS case) in how you are treating the boundary conditions before. I would suggest to open an issue and try to fix this to reach the same accuracy as for the FEniCS case without subcycling in a separate PR. Not sure whether this is actually possible with OpenFOAM: In FEniCS, I needed 2nd order FEM to do the trick with the flux. I have no idea about the capabilities of OpenFOAM and FV here.

[MakisH]

@BenjaminRodenberg any clarifications / updates on this? Otherwise, I would just close it as not planned, as it is currently unclear.

Note that, in the meantime, we changed the technical implementation of the boundary condition in this OpenFOAM case: #428 #501.