Solute Transport in a Porous Medium in the Presence of Oscillations

This paper presents an experimental study of transport of a solute (fluorescent dye Rhodamine B dissolved in water) in a porous medium in the presence of water oscillations. The porous medium is a rectangular cell containing cylinders whose axis was normal to the plane of the cell. The measurement technique used allowed us to measure the Rhodamine B mass transport rate and obtain an instantaneous and a steady streaming velocity field between the cylinders. The diffusion coefficient related to steady streaming has been shown to be a linear function of the Peclet number, evaluated from the fluid steady streaming velocity. At low dimensionless oscillation frequencies, there is a universal relation between the effective diffusion coefficient and Peclet number. At moderate dimensionless oscillation frequencies, the proportionality factor between these parameters increases with increasing frequency.