Pressure boundary conditions

mnolan93 · November 24, 2015, 18:36

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

sadjad.s · November 25, 2015, 02:47

hi mate,
pressure outlet is static pressure for flow going out of domain.
do you have any reverse flow?

mnolan93 · November 25, 2015, 03:28

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!

sadjad.s · November 25, 2015, 03:54

try using velocity inlet and then calculate delta P across domain.
how much is your error?

mnolan93 · November 25, 2015, 04:12

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...

mnolan93 · November 25, 2015, 09:22

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

November 24, 2015, 18:36	Pressure boundary conditions	#1
mnolan93 Member Martin Nolan Join Date: Dec 2014 Posts: 33 Rep Power: 11	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
sadjad.s Member sadjad Join Date: Jan 2012 Posts: 72 Rep Power: 14	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, 03:54		#4
sadjad.s Member sadjad Join Date: Jan 2012 Posts: 72 Rep Power: 14	try using velocity inlet and then calculate delta P across domain. how much is your error? __________________ ICEM, CFX and Fluent expert

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November 25, 2015, 09:22		#6
mnolan93 Member Martin Nolan Join Date: Dec 2014 Posts: 33 Rep Power: 11	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