Hi

How do you set boundary conditions to simulate impeller motion? I'm using cfx 4. The graphic interface promixus does it automatically but once you work directly with cfx it's no longer easy.

Assign a 3D patch to the block that contains the impeller. Then use the Grid Motion Parameters command to define it's rotation speed and axis.

Okay, thanks. But physically what does CFX do to set such conditions?

Regards

The solver treats the interface between the rotating 3D patch and the stationary 3D patch as a sliding unmatched grid. You have a choice to run the model in transient mode or in a quasi-static mode using the Frozen Rotor or the Circumferential Averaged method.