Setting Pressure Boundary Conditions in ANSYS CFX Pre

AS_Aero · February 22, 2017, 07:07

Hi All

I have a similar issue:

I am using a pipe flow where I have at inlet a mass flow rate of 2 L/min and an operating pressure of 6 bar and the flow is passing through a diffuser to the outlet atmosphere. So I would like to know what kind of BC'n can I give !
At the inlet I need to give this 6 bar or mass flow rate of the water
But at the outlet what pressure value should I specify
Also the reference pressure value ? I am confused about this pressure value thing.
This 6bar at the inlet is provided by a barometer reading just before the inlet of the pipe. That means its the operating pressure and it has a flow rate of 2 L/min.
Now what should I specify for the outlet BC'n. (The flow is into the atmosphere)

ghorrocks · February 22, 2017, 17:50

If it diffuses to atmosphere and atmospheric pressure is part of your simulation then use atmospheric pressure as the reference pressure. Then you can apply on the inlet either a flow rate of 2 L/min or a pressure of whatever the gauge pressure is. Note the flow rate boundary will be more numerically stable so I would use that if possible.

February 22, 2017, 07:07	Pressure Boundary Condition CFX Pre	#21
AS_Aero Senior Member Join Date: Mar 2013 Location: Germany Posts: 357 Rep Power: 14	Hi All I have a similar issue: I am using a pipe flow where I have at inlet a mass flow rate of 2 L/min and an operating pressure of 6 bar and the flow is passing through a diffuser to the outlet atmosphere. So I would like to know what kind of BC'n can I give ! At the inlet I need to give this 6 bar or mass flow rate of the water But at the outlet what pressure value should I specify Also the reference pressure value ? I am confused about this pressure value thing. This 6bar at the inlet is provided by a barometer reading just before the inlet of the pipe. That means its the operating pressure and it has a flow rate of 2 L/min. Now what should I specify for the outlet BC'n. (The flow is into the atmosphere)

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February 22, 2017, 17:50		#22
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	If it diffuses to atmosphere and atmospheric pressure is part of your simulation then use atmospheric pressure as the reference pressure. Then you can apply on the inlet either a flow rate of 2 L/min or a pressure of whatever the gauge pressure is. Note the flow rate boundary will be more numerically stable so I would use that if possible.