Define the non-dimensional cell Péclet number as a measure of the relative strengths of convection and diffusion:

where is characteristic length (voxel length).

With the power-law scheme, diffusion is set to zero when voxel Pe exceeds 10.

If 0 < Pe < 10, the flux is evaluated by using a polynomial expression. The net flux per unit area at the west control volume face:

for 0 < Pe < 10, and

for Pe > 10, where

The coefficients are given for

as