interior surfaces
 

Hi everybody

I am using ICEM as a mesh generator tool. I have a domain including different parts and blocks but all in one fluid body. I wish to define the surface between two adjacent parts as an interior.

I define two surfaces at the interface of two parts and faces are apparently coincide but each are in of the parts. Then I associate the face at the interface to both surfaces and then define both of them as interior.

When I export the file to the fluent. However, fluent changes these interiors as wall. How can I define these surfaces as interior?

Thank you for your helps in advance,