engleski

Numerical simulation of two-dimensional conservative solute transport

This paper presents numerical simulations of conservative solute transport in randomly heterogeneous porous media. Heterogeneity is associated with the hydraulic conductivity field, which is described as a random function with mean &micro ; ; _Y, variance σ ^2_Y, and isotropic correlation length λ _Y, where Y is the natural logarithm of 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 compositionally efficient manner. The large-scale spatial effects of the variable flow field on the developing solute plume are analysed. The spatial and temporal moments of the solute plume are examined. Results from numerical experiments are compared to stochastic theory predictions. From small variability in the hydraulic conductivity field the numerical results match predictions in the early stages, but for increased variability some non-ergodic effects are witnessed ; different realizations of the hydraulic conductivity field produce different plume developments. Stochastic theory predictions of asymptotic longitudinal and transverse mixing differ from some computational results. These differences are attributed to the small perturbation and stationarity assumptions introduced on the nonstationarity fields (e.g. concentration) by stochastic theory, and this behavior is made visible using an animation graphics technique developed at the Minnesota Supercomputer Institute.

numerical simulation; two-dimensional conservative solute transport; randomly heterogeneous porous media; convection and dispersion processes

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