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mixing length models and wall functions

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Old   April 2, 2007, 13:00
Default mixing length models and wall functions
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tiz
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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?
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Old   April 2, 2007, 16:38
Default Re: mixing length models and wall functions
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Mani
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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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