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librasu August 16, 2008 02:59

Periodic flow
Dear Everyone:

I am trying to simulate the axial flow pump, and it can be treated as a periodic flow. My problem is that the flow rate using periodic flow is much lower that the result when I simulate the entire model. The MRF method is used. /grid/modify-zones/make-periodic is used to create the periodic. Pressure inlet and outlet are the boundary conditions. Different regions are connected with interface (Periodic).

Is there anyone familiar with this kind of model? Can you give me any suggestion to solve this problem? Is there anything else I forget to set up?

Thank you in advance

Jason B August 18, 2008 12:24

Re: Periodic flow
Periodic case will only report the flow rate through that one passage. You'll have to multiply it by the number of passages to get the proper flow rate (so if it's a 20 blade compressor, and you modeled one passage, your actual flow rate will be 20x the calculated flow rate).

If that's not the fix, then you'll have to spend some more time digging through your model. Checking pressure / mach contours on the compressor geometry. You're looking for major differences that you can then trace back to a cause (i.e. if you notice flow isn't moving from one passage to another, then it's a problem with your periodic BC... or if your static pressures are way different at the exit, then it could be your exit BC... stuff like that)

Hope this helps, Jason

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