Taylor dispersion of particles in stratified media with random transition rates

The dispersion of particles in a stratified medium with a flow normal to the stratification is studied for the case when the transition rates between the various strata are random variables. One- and two-dimensional stratified systems are considered. The effective diffusion coefficient in the flow direction is computed numerically. The numerical results are compared with the predictions of a mean-field theory known as the effective (or coherent) medium approximation. (C) 1996 American Institute of Physics.