Multiple CAD Regions

I have been struggling for days to run my simulation. Any multi-part model I import (I have tried modeling with both Rhino3D and Blender) will not simulate using the incompressible analysis type and gets the following error message: “A setup with 2 regions is being used in a single-region analysis type. Please make sure that all regions except for one have an Advanced Concept assigned to them”. I have tried merging the two objects I have in the CAD programs, but Simscale still treats it as two objects (so it gives the error message). These test scenes are very simple: A box in another box.

How can I resolve this problem? What can I do specifically in either Simscale, Rhino3D, or Blender to make the simulation work in a model that has more than just one box?


It’s fairly simple. For all CFD-related analysis types (except for Conjugate heat transfer), we need only a single volume in the CAD model, representing the fluid region.

All solid parts should be removed from the model, otherwise they will cause multi-region mesh errors (except in special cases, such as simulations involving advanced concepts).

Therefore, in your case, all you have to do is to run a boolean operation (or mesh boolean operation, if it’s a .stl file), to subtract the solid part from the flow region, before importing the geometry to SimScale.

After you do that, the simulation should run normally.