Physical number in 3D msh

[senzhao]

why comes this error?I use Gmsh to create the msh,but always lead to this error.Thank you!

[Juan]

HI @senzhao

Thanks for trying the software. Every volume should have be assigned to a physical group. My understanding is that gmsh should automatically remove mesh elements that do not have a physical group assignment.

From https://gmsh.info/doc/texinfo/gmsh.html#Elementary-entities-vs-physical-groups:

By default in the native Gmsh MSH mesh file format (see Gmsh file formats), as well as in most other mesh formats, if physical groups are defined, the output mesh only contains those elements that belong to at least one physical group. (Different mesh file formats treat physical groups in slightly different ways, depending on their capability to define groups.) To save all mesh elements whether or not physical groups are defined, use the Mesh.SaveAll option (see Mesh options) or specify -save_all on the command line. In some formats (e.g. MSH2), setting Mesh.SaveAll will however discard all physical group definitions.

Please avoid the number 0 for a physical group assignment.

[senzhao]

Thank you for your reply.I tried to build one cylinder and it fits well in physical number(show no problems),but two cylinders show the same problem in physical number.
P.S. thank you for your advice.I will try to see if it can work.

[Juan]

Hello @senzhao

Here is an example for a cylinder within a cylinder using pygmsh with boolean operations.
https://github.com/devsim/devsim_misc/blob/main/gmsh/ring.py

There is a script in the same directory that handles adding the interface and contact boundary conditions:
https://github.com/devsim/devsim_misc/tree/main/gmsh