Absolute pressure

karlag · September 24, 2021, 07:14

Hi,

I'm using FLUENT 2020 R2 to simulate a flow.

For the inlet boundary condition, I'm using Pressure Inlet with 9 300 000 Pa for the Gauge Total Pressure, and for the outlet, I'm using Pressure Outlet with Gauge Pressure of 4 600 000 Pa.

I notice that the outlet pressure is the Absolute pressure (my reference value is 0). However, for the inlet the 9,3 MPa corresponds to the total (stagnation pressure = dynamic + absolute), but I want to ignore the dynamic. Is possible to set the absolute pressure at the inlet instead of the total?

Thanks for your help

LuckyTran · September 24, 2021, 14:19

Physically it is unrealistic (darn near impossible) to fix a static pressure at a flowing inlet unless the inlet is choked (i.e. Mach number equal to or greater than 1).

What you should do, is adjust your BC setting of total pressure such that you get the desired static pressure. Use the isentropic relations. You will of course need to know your inlet Mach number. Or you can just keep guessing until you get the right static pressure.

September 24, 2021, 07:14	Absolute pressure	#1
karlag New Member Karla Jacinto Join Date: Oct 2020 Posts: 5 Rep Power: 5	Hi, I'm using FLUENT 2020 R2 to simulate a flow. For the inlet boundary condition, I'm using Pressure Inlet with 9 300 000 Pa for the Gauge Total Pressure, and for the outlet, I'm using Pressure Outlet with Gauge Pressure of 4 600 000 Pa. I notice that the outlet pressure is the Absolute pressure (my reference value is 0). However, for the inlet the 9,3 MPa corresponds to the total (stagnation pressure = dynamic + absolute), but I want to ignore the dynamic. Is possible to set the absolute pressure at the inlet instead of the total? Thanks for your help

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September 24, 2021, 14:19		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65	Physically it is unrealistic (darn near impossible) to fix a static pressure at a flowing inlet unless the inlet is choked (i.e. Mach number equal to or greater than 1). What you should do, is adjust your BC setting of total pressure such that you get the desired static pressure. Use the isentropic relations. You will of course need to know your inlet Mach number. Or you can just keep guessing until you get the right static pressure.