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.
You are navigating away from the AIS Discovery experience