Incompressible converges, ideal gas goes nuts

psigcochair · January 13, 2010, 16:48

I'm flowing gas through some tiny inlets into a big nozzle. Incompressible converges, but when I switch to ideal gas, FLUENT has a coronary.

The velocities aren't very high, ~105 ft/s. I'm new to this, and any suggestions are greatly appreciated!

Thanks,
Michelle

herntan · January 13, 2010, 23:48

make fine meshes on inlet.

psigcochair · January 14, 2010, 08:48

The inlet mesh is very fine. The inlets are 0.032" diameter, and they have +100 faces/tets on them.

I believe the problem is when I switched to ideal, I received a warning (in the Check Case) that I had 0 gauge pressure at the boundarys. While the operating pressure was 95 psi. So I switched them, which was the WRONG thing to do!

Because my mach is <0.1 I should have left it the same. So I'd really like it if FLUENT wouldn't give me warnings that don't really apply to me. This is not the first time this has happened.

herntan · January 14, 2010, 21:14

you mean u change the operating pressure to 0psi and change the gauge pressure to 95psi ??

Fluent give this warning all the times. I don't think its a bad thing. People who understand what is operating pressure and what is gauge pressure should be understand what it trying to warn.

So does ur simulation works now?

January 13, 2010, 16:48	Incompressible converges, ideal gas goes nuts	#1
psigcochair New Member Michelle Join Date: Nov 2009 Posts: 5 Rep Power: 17	I'm flowing gas through some tiny inlets into a big nozzle. Incompressible converges, but when I switch to ideal gas, FLUENT has a coronary. The velocities aren't very high, ~105 ft/s. I'm new to this, and any suggestions are greatly appreciated! Thanks, Michelle

January 13, 2010, 23:48		#2
herntan Senior Member YH Tan Join Date: Mar 2009 Location: Malaysia Posts: 119 Rep Power: 17	make fine meshes on inlet. __________________ Herntan, Add Reputation if I am right

January 14, 2010, 21:14		#4
herntan Senior Member YH Tan Join Date: Mar 2009 Location: Malaysia Posts: 119 Rep Power: 17	you mean u change the operating pressure to 0psi and change the gauge pressure to 95psi ?? Fluent give this warning all the times. I don't think its a bad thing. People who understand what is operating pressure and what is gauge pressure should be understand what it trying to warn. So does ur simulation works now? __________________ Herntan, Add Reputation if I am right

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January 14, 2010, 08:48		#3
psigcochair New Member Michelle Join Date: Nov 2009 Posts: 5 Rep Power: 17	The inlet mesh is very fine. The inlets are 0.032" diameter, and they have +100 faces/tets on them. I believe the problem is when I switched to ideal, I received a warning (in the Check Case) that I had 0 gauge pressure at the boundarys. While the operating pressure was 95 psi. So I switched them, which was the WRONG thing to do! Because my mach is <0.1 I should have left it the same. So I'd really like it if FLUENT wouldn't give me warnings that don't really apply to me. This is not the first time this has happened.