SIMULTANEOUS VISUALIZATION OF WAKES AND INTERNAL WAVES GENERATED BY TOWED CYLINDERS IN STRATIFIED FLUIDS

摘要

Thin fluorescent dye layers were deposited in a stably stratified towing tank to visualize both the wake and internal-wave fields generated by horizontally towed cylinders. The wakes consist of laminar, vortex, and tubulent regimes, depending on the Reynolds number RD or an empirical stability parameter a which takes into account the effects of stratification. Internal waves generated by the towed cylinders and the laminar wakes are steady and stationary to the cylinder-fixed coordinates except for localized flows inside rotors formed at very low Froude numbers. Unsteady internal waves generated by vortex and turbulent wakes are two- and three-dimensional, respectively. Qualitative and quantitative information derived from the visual experiments is applied to characterize the generation and evolution of steady and unsteady internal waves.