[Gmsh] Clarification on Element Physical Group Relation

DILASSER Guillaume Guillaume.DILASSER at cea.fr
Fri Feb 21 09:04:22 CET 2020

Dear Xavier,

Physical groups are explained in Section 6.2 of Gmsh manual<http://gmsh.info/doc/texinfo/gmsh.html#Elementary-entities-vs-physical-groups>. The TL;DR is: when some part of the mesh (a node, edge, face or element) is part of a physical group, it is marked with a numerical “tag”. Constituents of the mesh can receive more than one “tag” when they belong to the intersection of different physical groups. The solver using the mesh then reconstructs the physical groups by looking for element carrying a certain tag.

As for the formatting of the .msh file, it is explained in Section 9.1 of the documentation<http://gmsh.info/doc/texinfo/gmsh.html#MSH-file-format>. The .msh file has a $Entities section in which you will find the mesh constituents (nodes, edges, faces and volumes) and each will be marked with the physical “tags” you defined in your .geo file.

Sincerely Yours,

Guillaume Dilasser

De : gmsh <gmsh-bounces at ace20.montefiore.ulg.ac.be> De la part de Xavier Johnson
Envoyé : vendredi 21 février 2020 02:58
À : gmsh at onelab.info
Objet : [Gmsh] Clarification on Element Physical Group Relation


I had some confusion when I assign a physical group in the gmsh program to how those physical groups relate to the generated mesh elements. This is more of a concern when I am trying to get an understanding on the information about the elements in the output .msh file.

Any clarification would be useful.

Thank you,
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