[Gmsh] Periodicity at the boundary of a box

[Rohracker, Maurice]

Dear GMSH developer and user,

for a HiWi job at the FAU Erlangen-Nürnberg we're using GMSH in PYTHON 
for meshing representative elementary volume (RVEs).

Therefore we have a box (2D) with circular inclusions. For the following 
FE simulation, we need periodicity at the boundary.

I was trying to use:     gmsh.model.mesh.setPeriodic(dim=2, [rveLine1], 
[rveLine3], affineTransform)
with an affine transform matrix np.array(([1., 0., 0., 0.,
                                            0., 1. 0., 0.,
                                            0., 0., 1., 0.,
                                            0., 0., 0., 1.]), float)

Or is it a good approach setting each point on the boundary to handle 
the desired number of elements on the boundary by oneself?

Could you help me set up the affine transform matrix (is there an 
example?) or are there any other and better way to get periodicity at 
the boundary?

Thanks a lot for your support in advance.

Kind regards,
Maurice Rohracker
Master Student Computational Engineering FAU Erlangen-Nürnberg