Ansys Employee

I'd probably look at solving this in 2d as there won't be much (any) flow in the z direction unless you're really interested in the end effects.  

If you do want 3d then read up on swept mesh and inflation: it's not set in the same way as an unstructured mesh. I'd also consider splitting the domain so you can concentrate mesh in the cylinder & wake region. Bodies of influence can cause some pretty big jumps in cell size so need to be used with some care.