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?

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.