Posted by ADSW1243 on
URL: http://forum.featool.com/Importing-gmsh-mesh-file-with-several-subdomains-tp315p327.html

For the STEP file discussed (consisting of a solid block with the coil placed inside, without any intersection/hole for the coils position), the commands suggested in GMSH produces a mesh with two analytically separated regions (which just so happen to overlap physically). This would be consistent with modelling the box as one complete physical system, and the coil as another complete physical system. The two are not inter-related or connected.

Typically I would use Coherence; after the merge .STEP file to produce a mesh consisting of a single domain. The GMSH physical groups option is then used to relate elements to sub-domains. Following this method produces the type of mesh I would usually work on for FEM modelling.

I have removed this command and indeed I see that the resulting .msh file can be correctly imported to the FEA Tool with two sub-domains. But before I can progress with this there are some concerns to address:

From the mesh generation standpoint, I am now generating two disconnected domains which happen to overlap at some points in space. I'm unsure how then the FEATool would model a coherent system on this disconnected mesh.
Further on this line, the GMSH optimisation procedures no-longer function on the geometry provided, I simply end up with a uniform mesh in each geometric entity because they're no longer connected. Even in the simplest case I would expect some sort of mesh graduation due to the relative size of the universe domain to the source domain.

In short - using your commands I'm telling GMSH that my .STEP consists of two domains. It then meshes the two domains separately and outputs those to the FEATool. This interprets the two domains as sub-domains correctly, but as far as I can tell the mesh it has imported for each region are not connected to each-other, and therefore any resulting analysis will also be disconnected.

If the Tool is interpreting the geometry first, and then forming a new mesh which is appropriate, that is fine but some additional details on what it is actually doing here and how I can control the optimisation would be important before I can decide to press ahead. Careful control of element sizes and shapes can be extremely important in accurate FEM analysis as I'm sure you're aware.

Assuming these concerns can be addressed, I'm looking forward to becoming a helpful member of the FEATool community and hope to have some useful contributions in the future.