This subnode should be used to model the heat transfer due to hydrodynamic mixing in a fluid flowing through a porous medium. It adds an extra term ∇ ⋅ (kdisp∇T) to the right-hand side of the heat equation in porous media, through the modification of the effective thermal conductivity keff with the dispersive thermal conductivity kdisp:

This section defines the Longitudinal dispersivity λlo and Transverse dispersivity λtr used for the computation of the tensor of dispersive thermal conductivity:

where Dij is the dispersion tensor

and λijkl is the fourth-order dispersivity tensor

When the Horizontal and vertical transverse dispersivities option is selected in the Define transverse dispersivity from list, the Transverse horizontal dispersivity λtr, h and Transverse vertical dispersivity λtr, v are defined instead of the Transverse dispersivity λtr.

In this case, it is assumed that z is the vertical direction and it defines the dispersion tensor as

Physics tab with Porous Medium selected in the model tree: