Urgent: Pump Boundary Condition

husker · January 9, 2012, 02:37

Hi all,

I'm on a centrifugal pump analysis. My boundary conditions are 1 atm absolute pressure at the inlet and 1.66 atm static pressure at the outlet. Rotating speed of the impeller is 2100 rpm.

As a result, I obtain negative mass flow rate at the inlet which means the fluid flows reversely.

Where am I wrong? What am I supposed to do in order to monitor mass flow rate under known pressure drop values?

Regards

LuckyTran · January 14, 2012, 00:37

A negative mass flow rate can mean that mass is entering the normal boundary. So the mass flow is going into your inlet. Are you sure your mass flow rate is reversed?

Fluent uses the outward facing normal convention for calculating fluxes.

shk12345 · January 14, 2012, 04:47

Sometimes when the flow is entering from the negative side of x,y or z axis fluent take it as negative mass flow inlet.

Check if that is the case in your situation

shk

January 9, 2012, 02:37	Urgent: Pump Boundary Condition	#1
husker Member Join Date: Mar 2009 Posts: 85 Rep Power: 17	Hi all, I'm on a centrifugal pump analysis. My boundary conditions are 1 atm absolute pressure at the inlet and 1.66 atm static pressure at the outlet. Rotating speed of the impeller is 2100 rpm. As a result, I obtain negative mass flow rate at the inlet which means the fluid flows reversely. Where am I wrong? What am I supposed to do in order to monitor mass flow rate under known pressure drop values? Regards

January 14, 2012, 00:37		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,668 Rep Power: 65	A negative mass flow rate can mean that mass is entering the normal boundary. So the mass flow is going into your inlet. Are you sure your mass flow rate is reversed? Fluent uses the outward facing normal convention for calculating fluxes. Last edited by LuckyTran; January 14, 2012 at 09:49.

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January 14, 2012, 04:47		#3
shk12345 Senior Member shoeb khan Join Date: Nov 2011 Posts: 179 Rep Power: 14	Sometimes when the flow is entering from the negative side of x,y or z axis fluent take it as negative mass flow inlet. Check if that is the case in your situation shk