does anyone have some further insights into how OGS5 computats the effective Diffusion coefficient? In the keywords it says
Fick’s law in the porous media (effective diffusion coefficient): \[ D^* = \omega \cdot D_d \] where omega is a coefficient that is related to the tortuosity (Empirical coefficient, lab: 0.5~0.01)
Is omega simply the tortuosity given in $TORTUOSITY ?
And is there a possibility to account for unsaturated cases, i.e. to make tortuosity a function of water content as e.g. in the Millington-Quirk relation:
tortuosity = (water content)^n / (porosity)^m
or is saturation accounted for once the mass dispersion tensor is computed?
(It seems so from the code in rf_mmp_new.cpp under MassDispersionTensorNew, but saturation is only a linear factor there… )