An Indirect Assessment on the Impact of Connectivity of Conductivity Classes upon Longitudinal Asymptotic Macrodispersivity

Solute transport takes place in heterogeneous porous formations, with the log-conductivity Y modelled as a stationary random space function of given univariate normal (pdf). For weak heterogeneity, the above mentioned quantities completely define the first-order approximation of the longitudinal macrodispersivity. However, in highly heterogeneous formations, nonlinear effects which depend on the multipoint joint pdf of Y, impact transport. The main aim of this study is to investigate the impact of deviations from the MVN structure upon asymptotic macrodispersivity. This is achieved by using the concept of spatial correlations of different Y-classes. It is found that the increased correlation in the low conductive zones with respect to the high ones generally leads to a significant increase in asymptotic macrodispersivity. The finding is explained by the solute retention occurring in low Y-zones, which has a larger effect on solute spreading than high Y-zones. Conversely, the asymptotic macrodispersivity decreases when the high conductivity zones are more correlated than the low Y-ones.