How does standard wall functions work
 

Hello all,

I'm trying to understand how standard wall functions work.
I have a dataset of a flat plate boundary layer, and I use information in the wall normal points to construct a coarse grid.
Let's take for eg: I have (y0, y1, y2..... Yn) in a fine grid.
I assume for a coarse grid, y3 to be the first grid point and calculate the quantities like gradient and wall shear.

Now I want to use wall functions in fluent ( standard) and see how much of an improvement there is to quantities like wall shear using the velocities.

However I am not able to see any improvement in the wall shear when I use the equations given in theory guide.

Any help would be appreciated to understand the concept.

Thank you