symmetry boundary condition

songpen1985 · October 10, 2012, 08:16

I am using symmetry boundary condition, which means I cut the domain into two pieces from the inlet to the outlet. I wonder if I should change the values of mass flow inlet, pressure outlet, hydrualic diameter, turbulence intensity. I know that I should change the value of mass flow inlet to its half, but how about pressure outlet, hydraulic diameter and other parameters? Should they be decreased?

Bionico · October 10, 2012, 09:36

Hi songpen,
I think that you should decrease only the mass-flow, the others are intensive property, they don't depend on mass or volume

regards

songpen1985 · October 10, 2012, 10:24

Thank you, Bionico! But if I use pressure inlet and pressure outlet, should I decrease the value because a higer total pressure gives rise to a higher mass in the system? Thank you.

Bionico · October 11, 2012, 02:11

You should not use pressure boundary condition for inlet and outlet as the Manual says (it's unstable), better using mass flow inlet & pressure outlet as you said before

Regards

sadjad.s · October 11, 2012, 03:16

Quote:

Originally Posted by Bionico

You should not use pressure boundary condition for inlet and outlet as the Manual says (it's unstable), better using mass flow inlet & pressure outlet as you said before

Regards

hi mates,
as i remember using pressure boundaries has no limit in fluent, but in CFX there was limitation of using total pressure boundary and static pressure.
also if you wanna use pressure inlet boundary, in symmetry, there is no need to decrease pressure.

songpen1985 · October 11, 2012, 08:14

Quote:

Originally Posted by Bionico

You should not use pressure boundary condition for inlet and outlet as the Manual says (it's unstable), better using mass flow inlet & pressure outlet as you said before

Regards

Hi, I am using a minus gauge pressure at the outlet to suck gas from a inlet so I need to use outlet pressure. If I use the symmetry boundary condition (then the outlet would be cut into half) and use the same minus gauge pressure, wouldn't the gas be sucked more from the inlet?

Thank you!

Bionico · October 11, 2012, 12:00

No, because there's a simmetry and FLUENT simulates the system taking into account this condition

Regards

beh70 · April 15, 2020, 03:08

hi
I am using symmetry boundary condition.for inlet, i used pressure inlet.should i decrease value of hydraulic diameter?

October 10, 2012, 08:16	symmetry boundary condition	#1
songpen1985 New Member Sean Join Date: Mar 2009 Posts: 15 Rep Power: 17	I am using symmetry boundary condition, which means I cut the domain into two pieces from the inlet to the outlet. I wonder if I should change the values of mass flow inlet, pressure outlet, hydrualic diameter, turbulence intensity. I know that I should change the value of mass flow inlet to its half, but how about pressure outlet, hydraulic diameter and other parameters? Should they be decreased?

October 10, 2012, 09:36		#2
Bionico Senior Member Flavio Join Date: Sep 2011 Location: Brescia, Italy Posts: 181 Rep Power: 15	Hi songpen, I think that you should decrease only the mass-flow, the others are intensive property, they don't depend on mass or volume regards soheil_r7 likes this. __________________ Bionico

October 11, 2012, 02:11		#4
Bionico Senior Member Flavio Join Date: Sep 2011 Location: Brescia, Italy Posts: 181 Rep Power: 15	You should not use pressure boundary condition for inlet and outlet as the Manual says (it's unstable), better using mass flow inlet & pressure outlet as you said before Regards __________________ Bionico

October 11, 2012, 12:00		#7
Bionico Senior Member Flavio Join Date: Sep 2011 Location: Brescia, Italy Posts: 181 Rep Power: 15	No, because there's a simmetry and FLUENT simulates the system taking into account this condition Regards __________________ Bionico

April 15, 2020, 03:08	symmery boundary	#8
beh70 New Member Join Date: Aug 2019 Posts: 3 Rep Power: 6	hi I am using symmetry boundary condition.for inlet, i used pressure inlet.should i decrease value of hydraulic diameter?

October 10, 2012, 10:24		#3
songpen1985 New Member Sean Join Date: Mar 2009 Posts: 15 Rep Power: 17	Thank you, Bionico! But if I use pressure inlet and pressure outlet, should I decrease the value because a higer total pressure gives rise to a higher mass in the system? Thank you.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Boundary Conditions	Thomas P. Abraham	Main CFD Forum	20	July 7, 2013 05:05
inlet velocity boundary condition	murali	CFX	5	August 3, 2012 08:56
Mixed/Robin boundary condition	aaev	OpenFOAM Bugs	2	December 15, 2011 14:03
Slip boundary condition what is inside	normunds	OpenFOAM Running, Solving & CFD	2	June 4, 2007 06:45
Regarding SYMMETRY boundary condition	Praveen Athanki	FLUENT	0	March 27, 2000 13:30