Naming surfaces in gmsh

[NoelGK]

Hi,

I am trying to import a mesh created in gmsh, with surfaces and volumes labeled also in gmsh, so that later I can define my regions using the syntax "vertices of group __" or "cells of group __". Nevertheless, with evey format that I have tried, I get the same error.

NotImplementedError: meshes with several cell kinds are not supported!

But this is not the case, I am not introducing triangles+tethrahedra, they are just 3-dimensional elements but with the surfaces labeled. Is it possible to import this kind of meshes? Which format should I use?

Thank you in advance.

[flothesof]

Hi @NoelGK

I have worked on this before, see this heat equation example: https://sfepy.org/doc-devel/examples/diffusion-time_heat_equation_multi_material.html#diffusion-time-heat-equation-multi-material

Regions are defined by tags as follows:

regions = {
    'Omega': 'all',
    'Omega_Cylinder': 'cells of group 4',
    'Omega_Powder': 'cells of group 3',
    'Omega_Plate': 'cells of group 1 +v cells of group 2',
    'Gamma_Plate': ('vertices in (z < -9.95e-3)', 'facet'),
    'Gamma_Source': ('vertices of surface *v r.Omega_Cylinder', 'face'),
}

To get this to work, I defined physical surfaces in the .geo file:

// Physical volumes
Physical Volume ("powder") = {3};
Physical Volume ("cylinder") = {4};
Physical Volume ("plate") = {1, 2};

And then exported them using the .mesh format, because msh22 or msh didn’t work for me.

// generate the mesh
// gmsh -3 -format mesh -o .\multi_material_cylinder_plate.mesh .\multi_material_cylinder_plate.geo

// convert to vtk format using sfepy
// sfepy-convert -d 3 .\multi_material_cylinder_plate.mesh .\multi_material_cylinder_plate.vtk

The full .geo file is in the sources here: https://github.com/sfepy/sfepy/blob/master/meshes/3d/multi_material_cylinder_plate.geo

Hope this helps.

Cheers,
Florian

[flothesof]

@rc maybe it would be nice to add explanations along what I wrote above to the doc, probably in this section https://sfepy.org/doc-devel/preprocessing.html ?

[rc]

Yes, it could go into the preprocessing doc - moreover many things can be done in a simpler way thanks to gmsh improvements.

BTW. the git version of sfepy does support meshes with several cell kinds, provided those have different topological dimensions (@vlukes am I right?).