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-   -   mixing length models and wall functions (http://www.cfd-online.com/Forums/main/13242-mixing-length-models-wall-functions.html)

tiz April 2, 2007 13:00

mixing length models and wall functions
 
I am using a mixing length model to simulate a turbulent flow in a duct. As i cannot go down to a y+ of the order of 1 (or however well into the viscous sublayer) for time constraints, I was planning to use a wall function to solve this. However, I read somewhere that ml models do not need wall functions. Anybody knows why is this?

Mani April 2, 2007 16:38

Re: mixing length models and wall functions
 
Of course, they don't "need" wall functions, if the grid is fine enough to resolve the boundary layer. The wall function itself is a semi-empirical relation based on mixing-length theory, but that doesn't mean you can choose cells of any size and still get the right shear stress.


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