Wave-Induced Streaming in Vertically-Excited, Stratified Fluids

Non-zero time averaged flows can be induced in fluctuating flows. Shimizu et al. found such time-averaged streaming to occur in stratified fluids excited in a vertical, stationary cylinder at a frequency close to the natural frequency of the axisymmetric interface wave [1]. PIV measurements have revealed intermittent formation of a stagnation region close the fluid-fluid interface that enables a jet-like flow departing from the center of the interface to be sustained over cycles. The jet-like flow induces a recirculating streaming flow that extends several diameters away from the interface. Difficulty still remains in quantifying experimentally the detailed flow structure and defining the driving mechanisms, since the streaming is more than one order of magnitude smaller than the forced oscillating flow. The present paper presents PIV data that show temporal evolution of the flow in each cycle, the effect of fluid viscosities and the excitation frequency and amplitude.