Pictures or Gifs on these kind of issues is always helpful! However from what I can see you already created a mesh so choosing a new refinement would not be possible right now. What you do is open the mesh tree and then select the dropdown menu of existing meshes and duplicate the one you already created. You should then be able to assign your region to the refinements you defined.
Also make sure that the material point is not inside your geometry and that your geometries are always watertight to avoid any problems during meshing.
Let me know if that makes sense - happy to help if thereâs anything that was not clear enough from my side!
I duplicated the mesh and tried to assign the refinement box as volume for region refinement, but still I cannot pick it. Attached I send you a screenshot.
I also double checked and the material point is outside the geometries but inside the background mesh box (wind channel), thatâs correct, isnât it?
For my other question: When I generated the mesh, it appears as shown in the second screenshot. Normally, the background mesh box (wind channel) should be meshed as well, shouldnât it?
Screenshot you attached shows correct behaviour: your mesh "geometry primitivesâ does contain ârefinement boxâ definition. In âRegion refinement 1â frame, you just switch the âsliderâ on: it is currently on, so region IS defined. You do not need to pick volumes. Kind of exception for mesh definitionsâŚ
Cheers,
Retsam
P. S. You need âexternalâ mesh, not âinternalâ for your CFD simulation. It should answer you second questionâŚ