[Gmsh] periodic BCs

[Danny Holstein]

All;

Let me try again.  How difficult would it be to modify GMSH to create a "Periodic Plane"?  Either a boolean switch could be set while doing a translate/rotate or the 2 planes could be grouped as a physical entity, which would be 2-D meshed once with the mesh elements copied to it's "periodic" brother.

Certainly, many problems have 180 degree rotational symmetry, and many RF devices (such as helix and coupled cavity TWTs and klystrons) have axial symmetry, magnetrons/CFAs have rotational symmetry to the vanes.  Mechanical structures with spokes would be greatly simplified with this symmetry.

It seems the switch used with a new "Periodic Plane" would be best, the translation matrix could be stored on generation and used immediately after mesh generation.

Thoughts?

   ...Dan