[Gmsh] Question related to periodic meshes on volumes

[Thierry J. Massart]

Hi,

First of all, congratulations for this nice tool !

I am trying to use GMSH to generate 3D meshes on periodic RVEs obtained 
from a 3D Voronoi tessellation. The translation from the tessellation to 
the GMSH .geo file is automated.

The cube is made of distinct volumic grains (i.e. volumes) such that a 
periodic geometry is obtained along 3 axes x, y, z. Such RVEs can be 
quite complex, with several hundreds of 'grains', and one of the faces 
of the cube can consist of many Line loops. A continuous 3D mesh is 
obtained using the 'Coherence' command.
My objective is to get a periodic mesh on opposite faces.

I read from several previous posts that extrusion followed by deletion 
of the generated volumes and lines could be a way to enforce 
periodicity. However, with the number of volumes and surfaces involved 
in the microstructures I deal with, this can become rather cumbersome.

My question is therefore whether there exists a possibility to enforce 
mesh periodicity along all three directions using the 'Periodic Surface' 
command.
If so, what is the meaning of the 'expression' field in the command 
synopsis from the user guide in that case ?

Many thanks your help!

Thierry

-- 
T.J. Massart
Associate Professor
Structural and Material Computational Mechanics
Building, Architecture and Town Planning Dept CP 194/2
Université Libre de Bruxelles (ULB)
Av. F.D. Roosevelt 50
1050 Brussels, Belgium
Tel: +32.2.650.27.42
Fax: +32.2.650.27.89
Email: thmassar at batir.ulb.ac.be