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-   -   wall functions and momentum (https://www.cfd-online.com/Forums/openfoam-solving/135147-wall-functions-momentum.html)

ebaldwin May 9, 2014 12:16

wall functions and momentum
 
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.

massive_turbulence May 9, 2014 17:02

Quote:

Originally Posted by ebaldwin (Post 490895)
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

ebaldwin May 10, 2014 07:48

Andrew,
Yes, that was exactly what I was looking for, thanks!
Eli


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