Support 3D cases

[BenjaminRodenberg]

Current handling of Quasi 2D - 3D cases:

To be able to support the 2D/3D coupling in the example tutorials/CHT/flow-over-plate/buoyantPimpleFoam-fenics we have to allow simulations, where the dimensionality is 3, even though there is no proper support for 3D simulations in the fenics adapter yet. See, for example

fenics-adapter/fenicsadapter/fenicsadapter.py

Lines 152 to 153 in 9ee7984

	elif self._dimensions == 3:
	return np.stack([vertices_x, vertices_y, vertices_z]), n

and

fenics-adapter/fenicsadapter/fenicsadapter.py

Lines 310 to 311 in 9ee7984

	if self._dimensions == 3:
	vertices_z = vertices[2, :]

If someone wants to run a "real" 3D simulation, the adapter does not work. We should either throw an exception in this case or implement a proper 3D treatment.

Update:

• Support 3D cases with the new modular design of the adapter.

[BenjaminRodenberg]

We are more and more getting into the situation that not supporting 3D leads to lots of corner cases that we have to catch. Example:

fenics-adapter/fenicsadapter/fenicsadapter.py

Lines 121 to 122 in 4feb7a4

	assert (self._fenics_dimensions == 2), \
	"Only 2D FEniCS solvers are supported. See https://github.com/precice/fenics-adapter/issues/1."

This becomes especially painful in the context of 2d/3d coupling. The many ifs and elses in this example are a nightmare.

I think that creating a real 3d case for the sake of validating our 3d implementation is probably a major task. However, we can already verify many of the required generalizations to go from 2d to 3d via tests (which do not harm in any case).

Therefore, I would suggest the following approach:

• Add tests for the different cases, where a special treatment of a 3d solver is necessary.
• Don't try to come up with a real 3d case (future work).
• Generalize the adapter to 3d.

[precice-bot]

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

https://precice.discourse.group/t/openfoam-fenics-for-fsi-on-3d/404/3