Dispersion in flow through porous media

Abstract

Dispersion is a consequence of flow. It results from the different paths and speeds and the consequent range of transit times available to tracer particles convected across a permeable medium. The kinematic mechanism stems from the connectivity structure of porespace; the dynamic mechanism, from the effect of pore shape and size on flow. Molecular diffusion can modify both. In many circumstances these mechanisms lead to distributions of macroscopic average solute or tracer concentration that are diffusive, i.e. that can be modeled by the convective diffusion equation, dispersion coefficients taking the role of diffusivity. For cases of diffusive mixing locally at pore junctions and no apprec..