Is there a 3D tutorial for gmsh and OpenFOAM?
 

I tried following the 2D tutorial and simply omitting the 2D changes that are made towards the end. The mesh looks fine and OpenFOAM has no problems with it when I convert it and inspect it with checkMesh, but I get very weird results when the calculation runs (i.e. airflows don't make sense, solution blows up). I believe the problem lies with the mesh because I have the same geometry with the same BCs, solver, etc., but with a different mesh and it works fine.

Changing the Recombination Algorithm to "Blossom" seems to fix this for me. No idea why.