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Impeller Efficiency Issue

Question asked by Marc C on Aug 8, 2012

I am trying to figure out the pump characteristics for this water pump I have created. I started out with just the inlet and outlet volume flows since I know what I what the outlet to be. After I got the numbers I wanted I then wanted to get the efficiency. I used the goals, pressure drop and efficiency equations from the rotating impeller tutorial to set up my simulation. After setting up all the goals and simulating I noticed that the outlet volume flow that I had originally gotten was now different. I was able to narrow down issue to the torque goal. If I turn on the torque goal I get a different outlet volume flow then when I suppress the torque goal. I get the same results if I use it for convergence or not. I was wondering if anyone has had this problem before or knows how to help. I don’t understand why the volume flow rate would change just by turning on and off the torque goal. 

My Setup is:

Analysis type Internal; Exclude cavities without flow conditions

Physical features Rotation: Type - Local rotating, Rotation axis - X

Default fluid: Water

Wall Conditions: Adiabatic wall, default smooth walls

Initial Conditions: Default conditions

Result and Geometry Resolution: Default