different flow rate, but same pressure gen. why?

Richard

First i am stimulating a pump. Therefore i use extrude to create a enclose area around the pump an cut the mat'l out, leaving behind a part with hole that take the shape of the pump inside

Then i spilt up the pump into stationary and rotating part, and use frozen rotor for the interface for them.I also create 2 cylindrical area, one as inlet flow area, another as outlet and use frozen rotor for their interface with the pump domain. I use mass flow rate for inlet and static pressure(refeence 0) for outlet.

I run this simulation for a different flow rate but get almost the same static pressure gen across the pump. How come? Inaddition there is high velocity found in at the interface.