Heterogeneity in Hydraulic Conductivity: Its Impact Upon Solute Transport and Correlation Structures

This study presents numerical simulation of conservative solute transport in randomly heterogeneous porous media. Heterogeneity is associated with the hydraulic conductivity field, which is described by three parameters: mean [mu]y, variance[sigma]y, and isotropic correlation length [lambda]y, where Y is the natural logarithm of the hydraulic conductivity. Transport simulations are performed using a particle tracking random walk (PTRW) method which is suitable for treating convection and dispersion processes in a computationally efficient manner. The objectives of this study are three-fold. First, the correlation structures of the velocity and concentration fields are analyzed as a function of the predefined [lambda]y Second, the large-scale, spatial effects of the variable flow field on the developing solute plume are analyzed. Third, nonergodic effects are investigated. The numerical results indicate that in most of the performed simulations nonergodic effects occur. Stochastic theory predictions of longitudinal and transverse mixing differ from the computational results. These differences may be caused by the highly anisotropic velocity correlation structure, which exhibits an apparent hole-effect in the transverse direction,