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-   -   Pressure Drop and Massflow rate issue (http://www.cfd-online.com/Forums/cd-adapco/56447-pressure-drop-massflow-rate-issue.html)

M February 11, 2008 16:44

Pressure Drop and Massflow rate issue
 
I'm a student who is using Star-CD for a university project on secondary flow in curved pipes. Currently I'm experiencing problems with a straight pipe with cyclic boundaries.

I am using the SIMPLE method with a residual tolerance of 1E-4. My mesh is 40*20 on the boundary faces and the simulation is run in mm.

I set the massflow rate for the straight pipe, and obtain a pressure drop from the boundary monitoring information in the .erd file.

I then input this pressure drop back into the straight pipe, but obtain a massflow rate out that is an order of magnitude higher than the original, despite all other flow conditions remaining the same.

Can anyone suggest what might be going wrong with my model? Thank you

Mangesh February 12, 2008 04:36

Re: Pressure Drop and Massflow rate issue
 
Hello,

take the mass average total pressure drop by post processing at outlet instead of monitoring info file


M February 12, 2008 10:23

Re: Pressure Drop and Massflow rate issue
 
I'm sorry, this may be obvious and I've missed it but how would i be able to do that? I've had a look at the post processing on the GUI interface.

Thanks again.

Tom February 12, 2008 17:31

Re: Pressure Drop and Massflow rate issue
 
! !-Calculate pressure at Inlet region: ! OPER,CLEAR,1,6 OPER,GETC,P,1 OPER,GETC,VOLU,2 OPER,MULT,1,2,3 BSET,NEWS,INLET VSET,NEWS,BSET CSET,NEWS,VSET,ANY CSET,SUBS,FLUID *GET,VOL1,RTOT,2 *GET,PRS1,RTOT,3 *SET,PIN,PRS1 / VOL1 ! !-Calculate pressure at Outlet region: ! BSET,NEWS,OUTLET VSET,NEWS,BSET CSET,NEWS,VSET,ANY CSET,SUBS,FLUID *GET,VOL2,RTOT,2 *GET,PRS2,RTOT,3 *SET,POUT,PRS2 / VOL2 ! !-Calculate the difference and list the result: ! *IF,PIN,GT,POUT,THEN *SET,PDIF,PIN - POUT *ELSE *SET,PDIF,POUT - PIN *ENDIF *LIST,PDIF


Anton Lyaskin February 13, 2008 10:12

Re: Pressure Drop and Massflow rate issue
 
The other option is to turn on average pressure calculation and flow rate calculation in "Engineering Behavior" for any boundary you need


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