I am trying to simulate air passing over a rotating cylinder in a box domain. I've created an inlet boundary and I've defined the cylinder as a separate wall boundary. My problem is that under define boundary regions, it's only allowing me to define either an inlet velocity or a rotating wall boundary, but not both at the same time. How can I solve this, so that I have both a rotating cylinder and an inlet velocity?

Many thanks for your help.

You can idetify each bounadry with different region number and each region can be assigned to different type such as inlet, outlet, pressure, wall etc. Then for each region, you can specify anything you want.