area weighted average

anif hidayatullah · April 7, 2010, 12:19

I am a student from Indonesia. Now, I conduct research on water liquid flow in porous media using fluent. I have a problem with my case. I use velocity inlet and pressure outlet the boundary condition.
velocity inlet = 8.5 m/s
pressure outlet = 0 pascal
after i simulate the case and confergence, then i see area weighted average for outlet. I was surprised, when I saw the pressure at the outlet -15 pascal. please help me? why?

thank's before

agd · April 7, 2010, 13:11

I don't use Fluent, but it sounds like you should interpret that as 15 pascals below the inlet pressure - that is, that's the pressure loss the system incurs in driving the flow. Most pressure-based solvers work with a relative, or gage, pressure instead of an absolute pressure. So negative pressures are not uncommon. Figure out what your pressure is relative to, and then get concerned if the absolute pressure in your flowfield is negative.

anif hidayatullah · April 7, 2010, 14:47

thank's agd
I'll check again, if the outlet pressure value relative to other pressures.

April 7, 2010, 12:19	area weighted average	#1
anif hidayatullah New Member anif hidayatullah Join Date: Apr 2010 Posts: 3 Rep Power: 16	I am a student from Indonesia. Now, I conduct research on water liquid flow in porous media using fluent. I have a problem with my case. I use velocity inlet and pressure outlet the boundary condition. velocity inlet = 8.5 m/s pressure outlet = 0 pascal after i simulate the case and confergence, then i see area weighted average for outlet. I was surprised, when I saw the pressure at the outlet -15 pascal. please help me? why? thank's before

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April 7, 2010, 13:11		#2
agd Senior Member Join Date: Jul 2009 Posts: 358 Rep Power: 19	I don't use Fluent, but it sounds like you should interpret that as 15 pascals below the inlet pressure - that is, that's the pressure loss the system incurs in driving the flow. Most pressure-based solvers work with a relative, or gage, pressure instead of an absolute pressure. So negative pressures are not uncommon. Figure out what your pressure is relative to, and then get concerned if the absolute pressure in your flowfield is negative.

April 7, 2010, 14:47		#3
anif hidayatullah New Member anif hidayatullah Join Date: Apr 2010 Posts: 3 Rep Power: 16	thank's agd I'll check again, if the outlet pressure value relative to other pressures.