Multi-Stage Compressor

cfdman · August 18, 2009, 01:58

Hey All,

There is a compressor which working in vacuum conditions. Also take N2 from 0.01 [mbar] (this is absolute pressure) and i want to model this in CFX.

My boundary conditions are;
inlet=0.01 mbar static pressure
outlet= 0.0125 kg/s
Pref= 0 [atm]

But pressure contours on CFX-Post i see negative pressure values about -2.5 [bar] this is physically not valid. Because environment is 0.01 [mbar] absolute pressure.

Does anyone have a suggestion for me?

Thanx

ghorrocks · August 18, 2009, 18:20

I assume you are running a compressible flow. I can't see how you would get negative absolute pressures as the density is undefined and therefore the solver would diverge. Are you sure you have your reference pressure set correctly?

Glenn

August 18, 2009, 01:58	Multi-Stage Compressor	#1
cfdman New Member Arda Ersan Join Date: Aug 2009 Posts: 13 Rep Power: 17	Hey All, There is a compressor which working in vacuum conditions. Also take N2 from 0.01 [mbar] (this is absolute pressure) and i want to model this in CFX. My boundary conditions are; inlet=0.01 mbar static pressure outlet= 0.0125 kg/s Pref= 0 [atm] But pressure contours on CFX-Post i see negative pressure values about -2.5 [bar] this is physically not valid. Because environment is 0.01 [mbar] absolute pressure. Does anyone have a suggestion for me? Thanx

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August 18, 2009, 18:20		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,830 Rep Power: 144	I assume you are running a compressible flow. I can't see how you would get negative absolute pressures as the density is undefined and therefore the solver would diverge. Are you sure you have your reference pressure set correctly? Glenn