# Wall modeling in LES

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 May 31, 2012, 13:20 Wall modeling in LES #1 New Member   Sarlak Join Date: Mar 2012 Posts: 18 Rep Power: 7 I,m trying to implement a wall model to my LES code with collocated grids. The target is to simulate flow over rough flat plate with zero pressure gradient. Now I have two questions. 1) I was wondering if I'm doing it correct: First I average the tangential velocities at 1st node above the wall, based on that I calculate the friction velocity $u_\tau$ using the roughness height, based on $u_\tau$ I find the wall shear. I introduce the wall shear into momentum equation via source terms and also modify the SGS viscosity at the wall using a one sided difference scheme for $\frac{\partial U}{partial y}$. To have zero overall pressure gradient I impose a pressure gradient to balance shear at the wall. (when I compare my results, it seems it's overpredicting the velocities at the wall and so I have a very small shear in the wall normal direction) 2) Are you aware of any specific difference between implementation of wall model in staggered and non staggered mesh arrangements? Thanks for reading this and I appreciate any replies. Hamid

May 31, 2012, 15:34
#2
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Filippo Maria Denaro
Join Date: Jul 2010
Posts: 3,753
Rep Power: 41
Quote:
 Originally Posted by chivaee I,m trying to implement a wall model to my LES code with collocated grids. The target is to simulate flow over rough flat plate with zero pressure gradient. Now I have two questions. 1) I was wondering if I'm doing it correct: First I average the tangential velocities at 1st node above the wall, based on that I calculate the friction velocity $u_\tau$ using the roughness height, based on $u_\tau$ I find the wall shear. I introduce the wall shear into momentum equation via source terms and also modify the SGS viscosity at the wall using a one sided difference scheme for $\frac{\partial U}{partial y}$. To have zero overall pressure gradient I impose a pressure gradient to balance shear at the wall. (when I compare my results, it seems it's overpredicting the velocities at the wall and so I have a very small shear in the wall normal direction) 2) Are you aware of any specific difference between implementation of wall model in staggered and non staggered mesh arrangements? Thanks for reading this and I appreciate any replies. Hamid
have you already read this issue on the book of Sagaut? you can find many references to dedicated papers

 Tags les, wall model, zero pressure gradient

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