SimScale CAE Forum

Problems with boundary conditions

This is my first simulation using SimScale. I’ve followed the tutorials, but I am getting 2 erros. I can’t run the simulation because of them. The errors are:

Wall 6 has face assignments that do not belong to a volume region


A setup with 8 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’m trying to simulate a car.

Any help would be great thanks

Hi @AmanG!

Always share your project link so that we can have a look at it! Awaiting your response :slight_smile:



Is this it?



Hi @AmanG,

Yes, this link works nicely! The setup currently contains two issues:

  • The first one is CAD-related. The CAD model that was imported contains a series of sheet parts, which are not desired for simulations:

In short, the volumes should be watertight & solid for simulations. As I can tell, the underfloor of your car consists of a simple sheet, so that’s causing issues. I’d recommend going back to your cad model and adding some thickness to the part.

For further information, please check this page.

  • The second problem is related to the enclosure operation. For Incompressible analysis, we need a single volume to run simulations (the flow region). The other solid parts should be removed from the geometry, otherwise they will cause a multi-region mesh error, which is the error that you ran into.

To solve this, please toggle off this option in the enclosure operation:

I’d recommend that you have a look at our external aerodynamics tutorial around a car, which will give you a good idea of the setup of this simulation.