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VEEBS September 24, 2001 02:43

making a rotating frame of Reference
 
Hi All, I am interested in simulating flow in a centrigufal compressor using CFX-TASCFLOW. Following are the conditions, what I applied for initial run. 1. rfr with specified omega 2. Walls stationary with relative frame of reference 3. Inlet with total pressure 4. Outlet with mass flow specified. I started with incompressible , turbulent flow, air is the fluid. I am not getting rise in pressure from inlet to outlet. What could be the casues ?

Thanks for your time. Veebs

Erich September 24, 2001 10:09

Re: making a rotating frame of Reference
 
Is your guess appropriate? Did it converge? What interface is it frozen or? What time step?

Robin Steed September 24, 2001 17:59

Re: making a rotating frame of Reference
 
Veebs,

How have you defined the inlet direction components?

Robin

VEEBS September 25, 2001 00:09

Re: making a rotating frame of Reference
 
Hi Erich /Robin, Thanks for your time. simulation aimed for only the impeller.So have one doimain defined as rotating. Solution is converged. But it shows decrease in pressure / total pressure from inlet to outlet. (no pressure rise). At the inlet, total pressure normal to the surface is defined. Thanks again Veebs

Robin Steed September 25, 2001 00:18

Re: making a rotating frame of Reference
 
Hi Veebs,

Defining the direction vector to be normal to the inlet face results in a vector which is normal to the face relative to the rotating frame, thus resulting in a high degree of pre-whirl and corresponding drop in pressure rise.

Re-define your inlet velocity components to be axial and you will get the pressure rise you expect.

Best regards, Robin

Drona September 25, 2001 06:09

Re: making a rotating frame of Reference
 
What about the direction of rotation? If you rotate it in wrong direction, you could get this problem. Give it a try.

Drona



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