# Periodic Vs symmetry Boundary conditions

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 June 6, 2013, 12:46 Periodic Vs symmetry Boundary conditions #1 New Member   Candy Join Date: May 2013 Posts: 12 Rep Power: 4 Hello, I would like to know the difference between periodic and symmetry boundary conditions? Thanks,

 June 6, 2013, 14:19 #2 New Member   Vishal Join Date: Feb 2011 Location: Bhopal, M.P. (India) Posts: 18 Rep Power: 6 Periodicity means that the thing or part is repeating itself. Eg: You can take single blade of a turbine runner and apply periodicity. Symmetry type boundary condition is applied if the geometry is exactly same about a plane. Ex: If you cut any body into exact half and place that body in front of a mirror, you are able to visualise the complete picture of the body. Amoul likes this.

 June 6, 2013, 19:25 #3 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,824 Rep Power: 85 You really should understand the mathematical basis of these boundary conditions. Read any CFD textbook for a description of this in detail, but in short a symmetry boundary has zero normal gradient for all variables except the normal velocity which is zero; and a periodic boundary just maps the values from one boundary across to another. Amoul likes this.

June 7, 2013, 00:02
Hi
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Dynampally Pavitran
Join Date: Mar 2010
Location: India
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Quote:
 Originally Posted by vishal.indomitable Periodicity means that the thing or part is repeating itself. Eg: You can take single blade of a turbine runner and apply periodicity. Symmetry type boundary condition is applied if the geometry is exactly same about a plane. Ex: If you cut any body into exact half and place that body in front of a mirror, you are able to visualise the complete picture of the body.
Vishal, both geometry and flow should be symmetric for symmetric boundary condition to be fully valid.

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