[akalopsis]

In my problem, I have a solid (heat sink) sitting on top of another solid (housing) and I have enclosed them both in a fluid domain since I am running a conjugate heat transfer analysis.

My issue is that when I'm trying to define the interface between the two solids, I cannot simple select where they are in contact, but rather only the entire face. The top face of the housing is in contact partially with the heat sink and partially with the surrounding fluid, but I can't define both or the interfaces will overlap.

This may seem like a simple problem, but I'm having a difficult time finding a solution online and it's messing up my solution. Any ideas?

Thanks in advance

[ghorrocks]

A boundary face cannot be shared between two interfaces. You are going to have to break the surface up.

[akalopsis]

Originally Posted by ghorrocks

A boundary face cannot be shared between two interfaces. You are going to have to break the surface up.

Thanks for the quick response Glenn. I kind of figured as much, so that's what I've been trying to figure out how to do (I'm new to CFD). At what stage in the pre-processing can this be done and how would I go about doing it?

[ghorrocks]

The best way is to go to the solid model and split the face. Then mesh with both faces given a different name, and then use the different faces in different interfaces in CFX-Pre.

[akalopsis]

Perfect. I went back into SolidWorks (where I imported the geometry from), split the faces, and now they can be easily selected in CFX-Pre. The only other problem that I am still having with my model is related to the heat generation boundary condition. My goal is to impose a heat flux on two faces of the model and then see how this heat is dissipated through the solid and out into the fluid. When I run the solution with this imposed heat flux though, I get unrealistically high temperature values and I don't know why.

I'm confident that all the other boundary conditions are correct because when I run the same analysis with a fixed temperature instead of a heat flux, the results make sense. If the faces in question are in contact with the fluid, do I apply the heat flux to both the solid and fluid domains on that face? The heat flux is approximately 69 000 W/m^2, which I calculated from the area of the faces and the desired heat power (112.5 W per face).

Any help/guidance would be appreciated.

[ghorrocks]

Have you done the normal accuracy checks: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

[akalopsis]

I just ended up using a fixed temperature, as it provided an adequate solution to my problem. That being said, I will take a look at that link in case I run into this problem in the future. Thanks again for your help.

[marcel_jay]

Originally Posted by ghorrocks

The best way is to go to the solid model and split the face. Then mesh with both faces given a different name, and then use the different faces in different interfaces in CFX-Pre.

Dear Glenn, have you any idea if there a possibilty to do this automatically in Designmodeler or so?
I have bodies with faces that are in contact with two other solids and one fluid. I was using the Named Selections based on the Auto Connections, which makes it even worse as multiple faces are grouped.
As my model consists of ~80 interfaces and the maybe more than 200 faces which would needed to be split up, doing this manually can't be the solution.

Cheers
Marcel

[ghorrocks]

Try the geometry and meshing forum.