This is regarding NekMesh utility. 

I would like to mesh a pipe which has coarse elements to begin with (inlet cross section shown in figure). In order to make the outer surface smooth I applied "spherigons" which worked fine (see attached). 

However, when I try to use "boundary layer splitting", NekMesh says:

No elements detected to split.

The element type on the outer surface are hexahedra. Is it the problem? 

Can anyone suggest a way out?