Boundary Conditions for centrifugal pump (or else...)
 

Hello,

I'm rather intrigued how little one can find about this. I have a model and mesh of a pump and I can't get the case to work, neither with MRF nor with dynamic mesh. I solved the problems with meshing because there are no more high pressure/velocity bearing spots and the results look smooth but the numbers are junk.

My first question is: what boundary conditions should I choose for inlet and outlet? What's the difference between my mesh with added movement/centrifugal force and an ordinary pitz-daily case? Why that worked but my case doesn't?

The second, more important question is: why? Why is it so important to set BCs right and how do I know what is right without a million aimless tries?