Vibrational Intensification of Mass Transfer Across the Interface Between Viscous Liquids

Abstract Vibrations are an effective tool for controlling fluid motion and mass transfer, in particular under microgravity conditions. The study addresses a topical technological problem: the intensification of mass transfer across the interface between immiscible high-viscosity liquids. The time-averaged flow in a flat vertical cell, generated by oscillations of a body at the interface between two viscous fluids, is investigated experimentally. The body has the shape of a parallelepiped elongated along the interface, with straight (beveled) edges. It is found that oscillations of the body perpendicular to the interface induce intense time-averaged flows in the form of a pair of large-scale vortices in each fluid, encompassing the entire cell volume. The flow direction is opposite to that of the known case of steady streaming in low-viscosity fluids. The dependence of the structure and intensity of the time-averaged flows on the vibration parameters is determined. It is shown that the detected time-averaged flow intensifies the mass transfer of a substance dissolved in one of the fluids across the interface; the mass transfer rate exceeds the diffusion rate by several orders of magnitude. The discovered vibration-induced effect is novel and can be effectively used in technological processes, in particular under reduced gravity conditions.