Hi all, I would highly appreciate it if someone can please tell me the difference between interface, internal and interior boundary types in Gambit. I like to specify contact resistance between two mating solids but not sure as to what boundary type should be selected for the interfacial boundary between them. Thanks very much.

Interface are usefull to "connect" 2 meshes which aren't connected (sliding mesh / moving mesh)

For Internal-Interior, I paste here, what Help provides: "The internal face boundary conditions are defined on cell faces, which means that they do not have a finite thickness and they provide a means of introducing a step change in flow properties. These boundary conditions are used to implement physical models representing fans, thin porous membranes, and radiators. The "interior'' type of internal face zone does not require any input from you. "

Thank you mAx. That was very helpful.