I have two different regions (porous and non-porous) and would like to simulate a flow in these two regions. In the porous region, i would like to use the Bruggemann correction (Deff =D*Porosity^1.5). Can i actually specify the diffusivity via the function DEFINE_DIFFUSIVITY and using Lookup_Thread(domain, id) to specify the zone which I hope to use the bruggemann correction? Need help on this.

Thank you.

yes, this is the right way.In DEFINE_Diffusivity macro you can specify different zones using the id of the zone and then for each of those zones you can return a value for the diffusion coefficient. About the correction I use that the 1/Deff=1/Dmol+1/Dkn.