# how to define the symmetric boundary condition for Menter's SST turbulence model?

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 November 22, 2012, 05:05 how to define the symmetric boundary condition for Menter's SST turbulence model? #1 New Member   Join Date: Nov 2012 Posts: 8 Rep Power: 4 hello, I am using Menter's SST turbulence model in the turbulent plate case described in http://turbmodels.larc.nasa.gov/flatplate.html. How should I define the boundary condition at the symmetric part before the flat plane. thanks, flyingseed

 November 22, 2012, 06:38 #2 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,916 Blog Entries: 6 Rep Power: 39 Use wall condition with zero shear.

 November 22, 2012, 08:16 #3 New Member   Join Date: Nov 2012 Posts: 8 Rep Power: 4 thanks for your reply. In process of solving the NS equations, it is OK that the no shear wall boundary condition can be applied. But in turbulent models, the variables are 'k' and 'omega', how can I define the no shear wall boundary? could you explain it more clearly? flyingseed

 November 22, 2012, 08:19 #4 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,916 Blog Entries: 6 Rep Power: 39 which solver you are using?

 November 22, 2012, 08:33 #5 New Member   Join Date: Nov 2012 Posts: 8 Rep Power: 4 you mean NS equations part? WENO5 for convective terms and 2nd center scheme for viscous terms. And for turbulent models, 1st upwind scheme for convective terms and 2nd center scheme for diffusion terms. Thanks flyingseed

 November 22, 2012, 09:06 #6 Super Moderator     Sijal Ahmed Memon (turboenginner@gmail.com) Join Date: Mar 2009 Location: Islamabad Pakistan Posts: 3,916 Blog Entries: 6 Rep Power: 39 Apply the wall boundary condition at the part of wall with zero shear (slip). Treat the plate as no slip boundary

 November 22, 2012, 09:59 #7 New Member   Join Date: Nov 2012 Posts: 8 Rep Power: 4 yes, I did as you said in solving the NS. When solving the laminar plate, I got good results compared with the Blasius solution. But when I turn on the turbulence model, the eddy viscosity(turbulent viscosity) is somewhat smaller than the results given in the nasa website. After checking every part of turbulence model, I found the symmetric boundary conditions before the plate for the turbulence model equations had very previous effects on the turbulent viscosity. So I am wondering which boundary condition should I adopt? thanks, flyingseed

 November 23, 2012, 09:45 #8 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,098 Rep Power: 19 A symmety boundary condition is applied by setting the wall-normal gradient of the variables to zero.

 November 24, 2012, 03:53 #9 New Member   Join Date: Nov 2012 Posts: 8 Rep Power: 4 thank you. I am trying this way. hope it works. flyingseed

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