Implementing Wall Functions for Turbulent Flows

How to implement Wall functions for turbulent flows?

The wall functions are applied only in the first layer of cells from the wall.
For standard or non-equilibrium wall functions, the mesh is coarse enough so that the first layer of cells covers most of the boundary layer.
When using the enhanced wall treatment, in which case the mesh actually resolves the boundary layer region, there is an additional procedure which takes into account the special calculations in the turbulent boundary region.

A Reynold number, based on the distance from the wall, is computed dynamically by the code and for cells with Re<200, the turbulent diffusivity is computed in a different way than in the core region.