Howto importing fluent mesh with internal walls
From OpenFOAMWiki
OpenFOAM does not know about internal walls, so if you have a doublesided wall (with cells on both sides) you have to work on the mesh before using fluentMeshToFoam:
1) Change all the internal walls to type "internal" (it's just a marker to find the relevant cellset in OpenFoam). Take care that you don't combine internal and external walls in the same boundary. 2) Save the mesh in Gambit with type "Fluent 5/6" as msh. 3) Use fluentMeshToFoam:
