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-   -   Symmetry Boundary Condition (http://www.cfd-online.com/Forums/cfx/100104-symmetry-boundary-condition.html)

StefanG April 20, 2012 08:14

Symmetry Boundary Condition
 
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

Far April 20, 2012 09:52

specify half

lffabiani April 20, 2012 10:13

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...

Lance April 23, 2012 02:18

http://en.wikipedia.org/wiki/Intensi...ive_properties

StefanG May 1, 2012 02:17

Thank you for your help!

hhh August 30, 2012 09:06

boundary condition (symmetry vs periodic doubt)
 
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.

bratzinger August 31, 2012 04:25

Hi
Quote:

Originally Posted by hhh (Post 379501)
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 ... ;)

ghorrocks August 31, 2012 06:56

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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