A wall function is the set of mathematical relations used to obtain the boundary conditions for the continuum equations whereby:
- a consistent set of assumptions is made regarding the distributions of velocity, turbulence and other scalar quantities;
- it is assumed that the turbulence model is valid only outside the viscous-dominated region of the boundary layer and the viscous-affected region of the boundary layer is not resolved; and
- it is assumed that the centroid of the near-wall cell lies within the logarithmic region of the boundary layer.
The main advantage of using wall functions is the significant savings in terms of near-wall mesh resolution.