[robinfisichella]

I basically already posted this question, but no one wants to reply to it.

Lets say i have a wheel. The wheel rotates inside a wheel housing which envelopes the top 2/3rds of the wheel, leaving the bottom 1/3rd exposed to the airflow.

The wheel is rotating, the housing is not, but both are moving through the air at x m/s.

Now i want to model the effects of a rotating wheel on the airflow BUT NOT the flow inside the wheel housing, so only the bottom 1/3rd.

I dont really understand the concept of interfaces, frankly it seems there are too many types and the whole system is massively overcomplicated.

How do i go about creating an interface between the bottom opening of the wheel housing which separates the fluid region from a region containing no fluid, but at the same time allows the wheel to rotate inside the housing?

[bramv101]

why would you want to work with interfaces or even the area inside where there is no fluid domain.
Just use 1/3 of the wheel + a box of air around it and apply a custom function to this 1/3 wheel surface.