Surface mesh not respecting line elements when making conformal quad/tri mesh
 

Hi all,

I have been trying for a few weeks now to mesh a model of brain blood vessels, which I have added cylindrical extensions to the inlet and the two outlets (first picture). I want to make a hexa mesh in the cylindrical sections and a tetra mesh with prisms in the actual vessels since the geometry is complex and I want the interfaces between the two to be conformal.

Attachment 99001

I have tried to do this by meshing the hexa and tetra parts separately and use the merge nodes feature but I couldn't get all of the nodes to merge (see below)
Attachment 99000

I have now tried to do this by making the hexa mesh first and converting it to an unstructured mesh, and then making the surface mesh for the tetra part with the "Respect Line Elements" setting turned on. This has worked for one cylindrical extension but for the others the nodes at junction between the tris and quads do not coincide (see below). I can see there is in fact a line element there from the hex mesh although there is an imperfection where the nodes are red. On another outlet the same thing happens and there is no imperfection like this.

Attachment 99002 Attachment 99003

I would really appreciate any help on this issue, I've been banging my head against this wall for weeks now.

Thank you very much,
RomThay