boundary conditions for hub and shroud
 

Hey guys,
I am simulating a centrifual pump, but not so clear about the boundary conditions.
If it is a closed impeller, we should set hub and shroud as "relative velocity =0"? If open impeller, then hub and shroud are walls with "absolute velocity=0“？
Is this understanding right? Thanks!

In a closed impeller, shroud will at rest while hub rotating about the axis. And there is no shroud in an open impeller. However, hub also spins round the axis. So it should be given a velocity value. Generally, we will specify a rotation speed for the ratating domain.
I am not sure I got your idea, but wish it helps.

Hi rikio,
Thanks for your reply.
For a closed impeller, shroud will "at rest"? Why is that? isn't it rotating together with the blade?
Thanks again for your explaination~
jasmine

Hi,

Only hub and blade rotate in a wheel-spin-only pump. Mean, wheel is the only moving part. It is easy to see if there is tip clearance since shroud and blade are separated.