Setting pressure and temperature of the fluid

Krebs_C · January 14, 2015, 05:07

Hi,

I need your help for my degree work:

In this work I´m using Fluent 15.0 to simulate a laminar, steady flow over a mirror. The fluid is nitrogen (g). The simulation worked quiet well with the standard setting, but my problem is, that I have an operating pressure of 10bar and a temperature of 200°C. With these conditions especially the density of nitrogen raises enormously. And with this change the kinematic viscosity changes also. So this leads to other flow conditions, which have an influence to the flow. I tried to set the operating pressure (Define -> Operating Conditions -> Operating Pressure), but I think Fluent just calculates pressure differences, so it just adds the operating pressure at the end of the calculation and the density, or other material properties aren´t influenced by this setting. I also tried to set the density and viscosity of the fluid (Material -> Create/Edit -> Properties). But this led to a divergent solution.

So my question is, weather there is a way to simulate the real conditions.

I hope someone of you can help me.

Thanks,
Christopher

LuckyTran · January 14, 2015, 18:03

The operating pressure is not a passive property. You should be able to use it to simulate "real" gas properties. But you would need to make sure that your properties are specified as being pressure dependent in the first place.

Your divergence is probably a result of a poor initial guess or other numerical instability in your problem.

January 14, 2015, 05:07	Setting pressure and temperature of the fluid	#1
Krebs_C New Member Christopher Krebs Join Date: Jan 2015 Posts: 1 Rep Power: 0	Hi, I need your help for my degree work: In this work I´m using Fluent 15.0 to simulate a laminar, steady flow over a mirror. The fluid is nitrogen (g). The simulation worked quiet well with the standard setting, but my problem is, that I have an operating pressure of 10bar and a temperature of 200°C. With these conditions especially the density of nitrogen raises enormously. And with this change the kinematic viscosity changes also. So this leads to other flow conditions, which have an influence to the flow. I tried to set the operating pressure (Define -> Operating Conditions -> Operating Pressure), but I think Fluent just calculates pressure differences, so it just adds the operating pressure at the end of the calculation and the density, or other material properties aren´t influenced by this setting. I also tried to set the density and viscosity of the fluid (Material -> Create/Edit -> Properties). But this led to a divergent solution. So my question is, weather there is a way to simulate the real conditions. I hope someone of you can help me. Thanks, Christopher

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January 14, 2015, 18:03		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,672 Rep Power: 65	The operating pressure is not a passive property. You should be able to use it to simulate "real" gas properties. But you would need to make sure that your properties are specified as being pressure dependent in the first place. Your divergence is probably a result of a poor initial guess or other numerical instability in your problem.