rotating ring in Fluent
 

Hi everyone,
i'm trying to simulate an rotating ring with fluent, which is partly sticked into water. I'm trying to find out, how much water is transported above by the ring.

If i give a constant rotation to the ring, it starts with this speed and my global currant number becomes to great --> no simulation possible.

So: I'd like to accelerate it first up to my finally speed.

Please help me