I cant get meshing groups to work properly... Anyone has advice?

Hi all,
I am new to Salome, but up until here everything was great and very intuitive. What I am basically trying is to create simple CAD models, mesh them and do FEM stuff with them (mostly with ElmerFEM). And everytime I try, I run into a problem during meshing. So I and need to export my model, mesh with some other software and so on… I am sure it should work in Salome, so it would be great if somebody could help me out:
Very basic example case: I have been following this 4min video: Multibody mesh from Salome to Elmer FEM - YouTube
For this person, it works, but its also a 5 years old version.

So i basically try to create two cylinders with different diameter, and cut them such that I have two objects: the inner cylinder and a cylinder wall with finite thickness. I partition those two and arrive at one object with an inner surface at the desired place. Great! I explode the partition-object and can now select the sub-objects wall/inner cylinder as shown in the video. I then go to the meshing workbench. I create a new mesh and compute it with Netgen1-2-3D . Then I use the “groups from geometries” tool to create a group (volume) for the center and one for the wall. I get a nice continious mesh and with the groups I can check that indeed I have separate, but fitting, sub-meshes for wall and inner-cylinder. So everything is great? Not really. I know export the mesh as .unv file. And whereever I open it, it’s broken. ElmerFEMGUI knows the correct number of groups, but cant show which meshes belong to them. If I try to solve on the mesh, the solvers throws a broken mesh error. If you open the mesh somewhere else, e.g. FreeCad, the groups are gone/broken as well. Ok, at first I thought maybe there is just a problem with the export. But without the groups everything is fine. And also, when I try to mesh with GMESH in Salome (which I used to use beforehand), it never meshes the whole object but only on of the subgroups. So there really seems to be an issue with those and I cant figure out what is wrong? Is this known? Am I just doing it wrong? I followed exactly the steps in the video just to compare and what works for that person doesn’t work for me. Did something change with version and I need a different approach? Or is my installation somewhat broken? Or is it a windows <-> Linux thing?

Thank you very much and have a nice week! :slight_smile:

I had a look at the Youtube tutorial you shared and was able to reproduce the different steps with both meshers in SALOME 9.8.0: NETGEN (used in the video) as well as GMSH on Windows. Do you have the link to the second part of the tutorial ?

As you can see it from the screenshot below, Mesh groups from geometry are indeed automatically created and reflect in ElmerGUI, once exported to universal file format (.unv).

You can find the GMSH UNV file [1] and the HDF study [2].

All the same, even if this is out of topic, there is currently a known limitation with GMF export (.mesh) of meshes with groups if there is no geometry attached to these groups.

[1] ftp://ftp.cea.fr/incoming/y2k01/sf-68/Mesh_GMSH.unv
[2] ftp://ftp.cea.fr/incoming/y2k01/sf-68/multibody_study.hdf