How do I incorperate domain interfaces
 

I've modelled an open duct moving through an enviroment. However I need to simulate the presence of a fan in the centre if this duct so it performs a form of suction.

The current method I have been using is drawing a cylinder in DesignModeller in the centre of my duct. I name the two faces fan1 and fan2. With the wall as an opening.
I implement the domain interface to give a pressure drop between fan1 and fan2. The cfx setup seems successful but when it comes to solving I get an error.
The error comes from conflicting domains in 2 regions which I'm assuming is fan1 and fan2.

Can somebody provide reading material, video tutorial or advice on how to set this up adequately as I cannot find any information on how to do this.

Regards

A better way to do this may be to use a source term to model the effect of the fan. Then you do not need interfaces, and you have more flexibility in defining what you want to do with the flow. You can use this to model the entire fan performance curve (which is recommended if you do not know the exact operating point).