Porous Media UDF

Trident

Is it possible to solve the Brinkman equation for porous media with effective viscosity instead of fluid viscosity?

Eqn 2.145 of Principles of Heat Transfer in Porous Media, Kaviany, 2nd Ed. except that instead of fluid diffusivity, I want to use an effective diffusivity formulation, where

effective diffusivity = function of wall normal distance

The function is defined from empirical correlations.

If so, is it possible to write a user defined function so as to account for the effective diffusivity function for the diffusion term in the governing equations?