Meshing a 3d conical diffuser
 

Hi all, I would like some advice on the meshning of a 3d conical diffuser. Consider this: I meshed 3 volumes corresponding to the small diameter pipe (inlet), a second volume for the diffusing section and a third volume for the larger diameter (outlet). I have split the walls of each of these 3 volumes in 4 to be able to map the end cap faces of the diffuser to be able to use the map scheme when comes the time to mesh the volumes. So far so good.

My specific problem is that I am having using the boundary layers (b.l.). For instance when I attach a b.l. on the inside face of one volume (corresponding to inner wall of pipe) I cannot attach a b.l. on the adjacent inner face because of an overlap in b.l. A typical message ressembles to this:

ERROR Boundary layer b_layer.1 already attached to the edge.9:face.6 pair. This must be removed befor attaching other boundary layers.

A second issue is that due to high aspect ratio I would like to be able to modify the length of meshed volume in the axial direction (along the pipe's length). How can this be done in 3d.

Could someone give me some advice on these 2 problems?

Best Ragards, David