Comsol Help -- How to Enable Rotating?

[YURIIMkZERO]

Hi,
I'm a newbie at Comsol and want ask for guide how to fill something with fluid and make sphere rotate. My goal in creating system where one sphere contains second. Second sphere rotates on its axis. Volume between is filled with fluid.
I understand how to create spheres, but couldn't understand how to fill volume between them and make inner sphere rotate.

 

[DrClaude]

You can do this using a 2D-axisymmetric geometry, then setting the surface of the rotating sphere as a sliding wall with a given φ angular velocity.

As an exemple, you can look at Swirl Flow Around a Rotating Disc in the Application Library.