# Symmetry Boundary Condition

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 April 20, 2012, 08:14 Symmetry Boundary Condition #1 New Member   Join Date: Mar 2012 Posts: 27 Rep Power: 5 Dear all, I'm sorry I didn't find an explanation to my question in the ANSYS Help, so I have to ask here: When I'm using a symmetry boundary condition in my simulation, which divides my geometry in two equal parts, will I have to impose half of the mass flow or anyway the full mass flow as my boundary condition? Thank you in advance for your reply. Best regards, Stefan

 April 20, 2012, 09:52 #2 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,909 Blog Entries: 6 Rep Power: 38 specify half

 April 20, 2012, 10:13 #3 Member   Luis Filipe Fabiani Join Date: Apr 2009 Posts: 43 Rep Power: 8 Yes, Far is right. The mass flow must be proportional to the partion, meaning that if you divide the domain in two parts, the mass flow must be 1/2 of what it would be on the whole domain. If you divide it in 6 parts, it should be 1/6 of the total mass flow, etc...

 April 23, 2012, 02:18 #4 Senior Member   Lance Join Date: Mar 2009 Posts: 522 Rep Power: 11

 May 1, 2012, 02:17 #5 New Member   Join Date: Mar 2012 Posts: 27 Rep Power: 5 Thank you for your help!

 August 30, 2012, 09:06 boundary condition (symmetry vs periodic doubt) #6 Senior Member   kumar Join Date: Nov 2011 Posts: 115 Rep Power: 5 Dear friends, i am doing 3D wing analysis, i have doubt on boundary conditions in fluent ie both symmetry and periodic, anybody have the answer please let me know briefly,for what kind of purpose to use symmetry & periodic boundary conditions, please tell any example with problem.

August 31, 2012, 04:25
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Hi
Quote:
 Originally Posted by hhh Dear friends, ...for what kind of purpose to use symmetry & periodic boundary conditions, please tell any example with problem.
if u have e.g. a large cooler with periodic elements or pipes where u don't want to simulate large inflow regions to have the desired velocity profiles, u can simulate relative small meshes and that reduces the amount of time to process -> especially useful if u want to simulate lots of parameter variations(e.g. in a DoE project)

if your 3D-wing isn't symetric at all, then ...

 August 31, 2012, 06:56 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,665 Rep Power: 84 Mathematically a symmetry boundary is zero normal velocity and zero normal gradient on all other terms, and periodic boundaries have all values equal on the equivalent locations on both boundaries.

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