@jousefm @sjesu_rajendra
Hi, thanks for replying
I exported each of the radiator block six surfaces from the cad software separately and merged them with the rest of the car.
I still can’t select the radiator inlet in the surface result control method, since after the meshing, all porous block surface were grouped together as cell zone bounding faces:
The mesh refinement is the same as in the fs tutorial:
NB: I didn’t use the STL split operation, since that would explode all body parts surfaces (which have different mesh refinement levels and different boundary conditions). Unless there a way to split just one surface of a multi surface stl?

