Short-time asymptotics of hydrodynamic dispersion in porous media

Abstract

AbstractWe consider convection–diffusion transport of a passive scalar within porous media having a piecewise-smooth and reflecting pore–grain interface. The corresponding short-time expansion of molecular displacement time-correlation functions is determined for the generalized steady convection field. By interpreting the generalized short-time expansion of dispersion dynamics in the context of low-Reynolds-number flow through macroscopically homogeneous porous media, we demonstrate the connection between hydrodynamic permeability and short-time dynamics. The analytical short-time expansion is compared with numerical simulation data for steady low-Reynolds-number flow through a random close-pack array of mono-disperse spheres. The quadratic short-time expansion term of the dispersion coefficient closely predicts the numerical data for a mean displacement of at least 10 % of the sphere diameter for a Péclet number of 54.49.