Effective Macrodiffusion in Solute Transport through Heterogeneous Porous Media

Homogenization method is used to analyse the equivalent behavior of transient flow of a passive solute through highly heterogeneous porous media. The flow is governed by a coupled system which includes an elliptic equation and a linear convection-diffusion concentration equation with a diffusion term small with respect to the convection, i.e. a high Peclet number is considered. Asymptotic expansions lead to the definition of a macroscale transport model. Numerical computations to obtain the effective hydraulic conductivity and the macrodiffusivity tensor have been carried out via finite volume methods. Numerical experiments related to the simulations of solute transport have been performed comparing the heterogeneous medium to the corresponding effective medium. The results of the simulations are compared in terms of spatial moments, L errors and concentration contours. Results obtained from the simulations using the model obtained by the homogenization method show good agreement with the heterogeneous simulations.