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emueller May 5, 2009 11:08

Pressure Rise Error
 
Hello,

I am doing an analysis on cavitation in a pump. I set my outlet static pressure to be a certain pressure and define a velocity profile at the inlet. I then iterate on my outlet pressure until my inlet static pressure is what I want it to be (-5 psi).

With my cavitation off model, this has worked well. I get an outlet pressure of 80 psi and an inlet pressure of -5 psi, for a pressure rise of 85 psi.

However, with cavitation on, my inlet pressure will not change with differeing outlet pressures. My goal is to get an inlet pressure of -5, and to do this I have set outlet pressures at 80,70,60,50,and 40 psi. For each outlet pressure, the inlet pressure is at -11 psi. I know that with cavitation on, the pressure rise should not be 1-to-1 like it is with cav off, but my inlet pressure should not be unchanging.

I did not try any outlet pressures above 80 psi because it would not make sense that my cav on has a higher pressure rise than with cav off. Also, my model is well converged (with domain imbalances at or below 0.1%). I put a monitor point at inlet pressure and outlet massflow, and outlet massflow is what my calculated value is, and inlet pressure has leveled off before the run converges. I have tried with both low blend factor and high resolution schemes, and each time, I initialize my model with the results from the cav off run.

Anyone run into this before or have any ideas what's going on here?

Thanks,

Ed Mueller


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