# Pressure boundary conditions

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 November 24, 2015, 18:36 Pressure boundary conditions #1 Member   Martin Nolan Join Date: Dec 2014 Posts: 33 Rep Power: 3 Hi all, I need to calculate flow rate from a 2d pipe. The 'total' pressure difference between inlet and outlet is only 1 pascal. The pressure inlet be asks me to define total gauge pressure, which is fine. However outlet says only gauge pressure - I presume static pressure. Using a value of 1 pascal less than the inlet BC does not give me accurate results vs theoretical results. Can anyone advise? Thank you

 November 25, 2015, 02:47 #2 Member     sadjad Join Date: Jan 2012 Posts: 70 Rep Power: 6 hi mate, pressure outlet is static pressure for flow going out of domain. do you have any reverse flow? __________________ ICEM, CFX and Fluent expert

November 25, 2015, 03:28
#3
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Martin Nolan
Join Date: Dec 2014
Posts: 33
Rep Power: 3
Quote:
 Originally Posted by sadjad.s hi mate, pressure outlet is static pressure for flow going out of domain. do you have any reverse flow?

I have no reverse flow

Cheers!

 November 25, 2015, 03:54 #4 Member     sadjad Join Date: Jan 2012 Posts: 70 Rep Power: 6 try using velocity inlet and then calculate delta P across domain. how much is your error? __________________ ICEM, CFX and Fluent expert

November 25, 2015, 04:12
#5
Member

Martin Nolan
Join Date: Dec 2014
Posts: 33
Rep Power: 3
Quote:
 Originally Posted by sadjad.s try using velocity inlet and then calculate delta P across domain. how much is your error?
The delta P must be 1 :/ the error is 5 orders of magnitude as well...

 November 25, 2015, 09:22 #6 Member   Martin Nolan Join Date: Dec 2014 Posts: 33 Rep Power: 3 Is there anyway I can ensure that the Total pressure difference between the inlet and outlet is 1Pa? I seem to be getting big changes in pressures

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