Mechanisms of anomalous dispersion in flow through heterogeneous porous media

Abstract

We study the origins of anomalous dispersion in heterogeneous porous media in terms of the \nmedium and flow properties. To identify and quantify the heterogeneity controls, we focus on \nporous media which are organized in assemblies of equally sized conductive inclusions embedded \nin a constant conductivity matrix. We study the behavior of particle arrival times for different \nconductivity distributions and link the statistical medium characteristics to large scale transport \nusing a continuous time random walk (CTRW) approach. The CTRW models particle motion \nas a sequence of transitions in space and time. We derive an explicit map of the conductivity \nonto the transition time distribution. The derived CTRW model predicts solute transport based \non the conductivity distribution and the characteristic heterogeneity length. In this way, heavy \ntails in solute arrival times and anomalous particle dispersion as measured by the centered mean \nsquare displacement are directly related to the medium properties. These findings shed light on the \nmechanisms of anomalous dispersion in heterogeneous porous media, and provide a basis for the \npredictive modeling of large scale transport.