mergeMeshes with overset issue
- mergeMeshes uses built-in topology changes
- which uses geometric matching for processor faces
- which can go wrong if multiple faces have exactly the same face centre
- which can happen for overset cases (if e.g. same cell sizes used in background and foreground meshes)
workaround: slightly perturb one of the meshes, e.g.
mpirun -np 12 transformPoints -scale 1.000171