The method to create a hybrid mesh.
Originally Posted by PSYMN
You need to create some construction geometry between where you want the two types of mesh (a cylinder in this case). Then generate a tetra mesh on the outside and a hexa blocking on the inside. It is important that this construction geometry be uniquely named and that both mesh types are projected to it and its perimeter... Then go to Edit Mesh => Merge => Merge meshes. You can check the help from there to get the rest of the way.