Ducted propeller- Wall/Interface?
 

Hello all,

I'm pretty new to the CFD so I'll appreciate if you would try to explain the things as simple as you can.

I've tried to simulate a propeller without a duct. I've created 2 domains, one is the surrounding fluid and the other is a smaller domain which rotates (using moving ref frame) close to the propeller. In this case I've managed to set the interfaces.

Now I'm trying to add a duct (axial cylinder around the propeller) to the model. The duct isn't connected to the propeller, there's a small gap between the inner diameter of the duct and the diameter of the propeller. I've tried to do the same thing as with the non-ducted propeller geometry:

1. Subtract the propeller from the inner (rotating) domain.
2. Subtract the duct from the surrounding domain.
3. Subtract the inner (rotating)+ propeller from the surrounding domain.

The problem that I've faced is that I can't use the duct both as a wall and a interface between the surrounding domain and the inner domain.

Thank you in advance.