# wall functions and momentum

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 May 9, 2014, 12:16 wall functions and momentum #1 New Member   Eli Baldwin Join Date: Aug 2013 Posts: 9 Rep Power: 11 Can someone explain to me if and how wall functions feed back into momentum? I am simulating turbulent nozzle flow with k-epsilon. The first cell sits around y+ of 30, and I am using kqRWallFunction, epsilonWallFunction, and mutWallFunction. I don't see where / how the law of the wall is being applied to U.

May 9, 2014, 17:02
#2
Senior Member

Andrew Somorjai
Join Date: May 2013
Posts: 175
Rep Power: 11
Quote:
 Originally Posted by ebaldwin Can someone explain to me if and how wall functions feed back into momentum? I am simulating turbulent nozzle flow with k-epsilon. The first cell sits around y+ of 30, and I am using kqRWallFunction, epsilonWallFunction, and mutWallFunction. I don't see where / how the law of the wall is being applied to U.

I'm guessing this is explained

"Of course the velocity in the first interior grid point is calculated through the solution of the velocity field. In the law of the wall / or any other wall function, you would like to set the velocity in the first grid point, because you know the velocity in that point based on theory. This is where the extra source term for the calculations comes in, in the case of openfoam, this source term is inserted into the momentum equation through nut/mut at the wall, as mut/nut at the wall are generally zero, due to the fact that k is zero."

here...
http://www.cfd-online.com/Forums/ope...ntation-2.html

Hope it helps!

Andrew

 May 10, 2014, 07:48 #3 New Member   Eli Baldwin Join Date: Aug 2013 Posts: 9 Rep Power: 11 Andrew, Yes, that was exactly what I was looking for, thanks! Eli