added tutorial for foam-extend

[hoehnp]

I added a modified version of the quickstart tutorial for foam-extend with the purpose of testing the foam-extend adapter.

[MakisH]

Thanks for the contribution! A first quick review of the changes, without having tried to run the code.

We generally have alternatives for the perpendicular-flap tutorial (which is meant to be something to copy from), not for the Quickstart (which is meant to be a specific first case to run). With that said, I do understand that this is a minimal case for you.

Since the changes are very minimal, I wonder if we could make the original case compatible with foam-extend, even if we just applied a small patch automatically. Some of the changes for foam-extend should still work with OpenFOAM (e.g., the noSlip/zeroGradient or the path of the preCICE config) or not be that relevant (e.g., the forces function object).

---

List of differences compared to fluid-openfoam:

0/U:

- type            noSlip;
+ type            zeroGradient;

dynamicMeshDict:

- motionSolverLibs ("libfvMotionSolvers.so");
+ motionSolverLibs ("libfvMotionSolver.so");

+ diffusivity uniform;

controlDict:

  libs
  (
+    "libforces.so"
+    "liblduSolvers.so"
     "libpreciceAdapterFunctionObject.so"
  );

• forces function object configuration (do we actually need that?).

fvSchemes:

-     div((nuEff*dev2(T(grad(U))))) Gauss linear;
+     div((nuEff*dev(T(grad(U))))) Gauss linear;

fvSolution:

     p
     {
         solver           GAMG;
         tolerance        1e-6;
         relTol           1e-4;
         smoother         DICGaussSeidel;
+        agglomerator    faceAreaPair;
+        nCellsInCoarsestLevel 10;
+        mergeLevels 1;
     }

preciceDict:

- preciceConfig "../precice-config.xml";
+ preciceConfig ".."/"precice-config.xml";

[MakisH]

Looking good, just needs some comments.

[MakisH]

Thank you once more for the contribution. I have added some documentation, and I think that this is now ready to merge.

Note that this tutorial is not meant to provide alternatives (and this is why we should not have an alternative folder - I missed the context when we talked in person). A better tutorial to have a foam-extend alternative for would be the perpendicular-flap. However, since foam-extend can be seen as an alternative version of the same solver, and since this is a test case for you, I see the value and I hold back my general objection to modifying this tutorial.

I also notice now that the "porting" script is actually in the tools/, so it is rather reusable across tutorials. This is a great step in the right direction. As a user, I would expect an overview of needed configuration changes in the adapter documentation (currently the best place would be https://precice.org/adapter-openfoam-support.html, which is sourced from the openfoam-adapter repository).