Advection describes the passive movement of a substance (or heat) with the moving fluid. Purely advective transport leads to a displacement of material particles with the distance velocity v of the water in the direction of the flow vector.

Consideration of purely advective mass transport

The equation for the advective mass flow j_adv is as follows:

j_adv = vc

With:

v = distance velocity [m/s]

c = concentration of the dissolved substance [kg/kg]

The distance velocity v results from the quotient of the filter velocity v_f and the porosity n:

Diffusion