SimScale CAE Forum

Multiple boundary conditions when only one is assigned to a face

Multiple boundary condition or interface assignments for the following entities: face79@Battery-14__Battery-13__Battery-12__Battery-11__Battery-10__Battery-9__Battery-8__Battery-7

I am analysing a flow in a room where there are batteries generating heat using conjugate heat transfer. I created a flow region and left existing parts there. I set up my simulation(inlet outlets and walls). When I try to set up a fixed temperature for any face of my 8 batteries using wall I get an error message. I have triple checked the boundary conditions and the batteries do not have any boundary conditions assigned to anywhere else. Would there be another reason why I would be getting this error message. I assigned one boundary condition to a face.

Hi @ialhassan ,

The linked project seems to be private, so I can’t know for sure what is wrong. Based on your description, you probably defined a boundary condition to an interface, which is not allowed.

Please refer to figure 6 from this documentation page for more insights.

PS: a couple of ways around it:

  • Since the battery walls are at a fixed value anyway, you could potentially remove the batteries from the CAD model after generating a flow region, and set the fixed value boundary conditions directly to the flow region. Without the batteries, you won’t have an interface anymore.
  • You could also carve a “void” inside the batteries, assigning a fixed temperature condition to the inner face. The objective here is to avoid having an interface to allow you to set a boundary condition


Just made it public. If you can take a look.

Thanks, my original assumption was correct:

Is this intended?

No it was not intended. But when I creat a flow region, the whole flow region is one construct so I can only assign one boundary condition to it. Would there be a different way to fix it?

Hi, it’s necessary to remove the “face79@battery-14(…)” assignment from the Wall 3 boundary condition. The other conditions can remain as they are.

yeah but I need those batteries at a fixed tempertaure or a constant heat flux. So if I removed them it would defeat the purpose of the simulation. Please advise

Please refer to my first response :slight_smile: