Hi all trying to simulate simple centrifugal water pump I noticed strange problem. I set up geometry (with opening BC at inlet, pressure at outlet and given rpm. to see suction at the inlet). The frozen rotor approach was used. The problem is that as long as using rather not dense mesh I noticed good consisteny with analytical caluculations in terms of flow rate. When I try to "dense" mesh (to perform mesh study) my flow rate increases twice. Of course boundary layer and so on are still there.

Any comments? Luk

Why not try to model the inlet as a total pressure inlet instead of an opening, and specify the mass flow rate at the outlet to see if you get the correct pressure rise? Depending on the location of your point on the pump curve, this may be more stable.

I would think that a total pressure inlet should be used instead of an opening, regardless of where on the pump curve you are operating.