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agg May 2, 2005 17:29

Wall functions - iterative approach
 
Hello,

I am using LES for my flow. I am not resolving near wall structures and hence trying to use the wall function approach, i.e. using

u/ut = 1/0.41 * ln(y*ut/nu) + 5.2

Here, u and y are the streamwise velocity and distance of the grid point nearest to the wall. nu is the kinematic viscosity.

In the above equation the only unknown is friction velocity ut:

ut = sqrt(tau_w/rho) where tau_w is the wall shear stress and rho is density

Does anyone have any experience with the methods (iterative) used to obtain ut?

Thanks

-agg

etyo May 13, 2005 12:25

Re: Wall functions - iterative approach
 
I have faced the same problem before but I was dealing with RSM and not LES, the procedure is straight forward. Guess one value of Ut (on the right hand side) and iterate till you get the same value on the left hand side. You might need to use the length scale from the mixing length theory as the minimum allowable length (by using the MIN function). If you still facing problems I suggest you to consult Prof. Lars Davidson (lada@tfd.chalmers.se).


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