Examination of stochastic dispersion theory by MRI in aperiodic porous media

Magnetic resonance imaging techniques were applied to obtain concentration and velocity field measurements during flow in an aperiodic heterogeneous p orous medium. These measurements were used to evaluate the applicability of a stochastic perturbation theory and the validity of the assumptions under lying its derivation. A comparison of experimental moment data to the first and second moments of simulated mean concentration distributions showed th at the theory did not match the experimental data. While the results showed general agreement, the stochastic model appeared to slightly overpredict t he experimentally observed mixing behavior Discrepancies between experiment al and numerical results were attributed to the assumption that triplet cor relation terms involving fluctuating velocities and fluctuating concentrati on ape insignificant relative to terms containing doublet cross-correlation s. Measured velocity covariances were compared to the velocity covariance d etermined front the first-order solution to the flow equation. The first-or der relation agreed generally with the measured covariance, but did not acc urately predict the detailed covariance structure in the aperiodic heteroge neous model.