Numerical analysis of the effects of heterogeneities on dispersion

Abstract

The effects of heterogeneities on macrodispersion in porous media were investigated using numerical simulations. Cases involving a single heterogeneity were investigated initially. The size and location of the input source strongly influenced the magnitude of the longitudinal macrodispersion coefficient. A smaller solute input source decreased the longitudinal macrodispersion coefficient when the source was located up gradient from the heterogeneity and was not centered (vertically). A vertical flow component reduced the magnitude of the longitudinal macrodispersion coefficient in all cases, and asymptotic dispersion coefficients were approached at an earlier time than those without vertical flow. Dispersion in stratified porous media was also simulated. Cases involving both a vertical flow component and no vertical flow were studied. The asymptotic longitudinal dispersivity values are in close agreement with stochastic solutions, as long as certain conditions are met. Transient flow conditions were also shown to strongly influence dispersion.