Setting up an initial pressure in FLUENT 16.1

ColinHahn · July 12, 2016, 10:23

Hopefully this is an easy question:

I am trying to model air flow through a simple pipe. I am assuming the flow will be turbulent based upon hand calculations, so I am modeling it that way.

I am trying to make my initial pressure at the inlet 50 PSI and my initial outlet pressure at 0 PSI. Both of these are gauge pressures. I have tried reading the user manual, but I am still unclear of what I need to do to accurately model what I want.

What is the difference between Total Gauge Pressure and Supersonic/Initial Pressure?

Do I set both of these to 50 PSI to model the conditions I want above?

The analysis is using pressure inlet if that helps and is being done in 3D.

LuckyTran · July 13, 2016, 02:44

Nearly all pressures in Fluent are gauge pressures (except for the absolute pressure, and operating pressure which is used to specify the reference gauge).

The supersonic gauge pressure is only needed if the inlet is supersonic. If the inlet is subsonic, the supersonic gauge pressure is ignored and you can put in any value. However, initial gauge pressure is utilized if you use the compute from option in the initialization step. Hence it's labeled supersonic / initial gauge pressure. The total pressure is the stagnation pressure from fluid mechanics, it is not the static pressure.

You cannot impose a static pressure at an inlet, you may only impose a stagnation pressure.

Is the inlet 50psig or 50psia, and the outlet 0 psig or psia? Pressure inputs in Fluent are gauge pressures and the default reference pressure is 101325 Pa. So you would need give the appropriate value.

July 12, 2016, 10:23	Setting up an initial pressure in FLUENT 16.1	#1
ColinHahn New Member Join Date: Jul 2016 Posts: 1 Rep Power: 0	Hopefully this is an easy question: I am trying to model air flow through a simple pipe. I am assuming the flow will be turbulent based upon hand calculations, so I am modeling it that way. I am trying to make my initial pressure at the inlet 50 PSI and my initial outlet pressure at 0 PSI. Both of these are gauge pressures. I have tried reading the user manual, but I am still unclear of what I need to do to accurately model what I want. What is the difference between Total Gauge Pressure and Supersonic/Initial Pressure? Do I set both of these to 50 PSI to model the conditions I want above? The analysis is using pressure inlet if that helps and is being done in 3D. Last edited by ColinHahn; July 12, 2016 at 10:39. Reason: Forgot some information

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July 13, 2016, 02:44		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,672 Rep Power: 65	Nearly all pressures in Fluent are gauge pressures (except for the absolute pressure, and operating pressure which is used to specify the reference gauge). The supersonic gauge pressure is only needed if the inlet is supersonic. If the inlet is subsonic, the supersonic gauge pressure is ignored and you can put in any value. However, initial gauge pressure is utilized if you use the compute from option in the initialization step. Hence it's labeled supersonic / initial gauge pressure. The total pressure is the stagnation pressure from fluid mechanics, it is not the static pressure. You cannot impose a static pressure at an inlet, you may only impose a stagnation pressure. Is the inlet 50psig or 50psia, and the outlet 0 psig or psia? Pressure inputs in Fluent are gauge pressures and the default reference pressure is 101325 Pa. So you would need give the appropriate value.