TURBULENCE AND MIXING IN A STRATIFIED SHEAR-FLOW

The characteristics of turbulence in the upper mixed layer and the nature of the sheared density interface of a two-fluid system, with a driven upper layer and a stagnant lower layer, were studied experimentally. The experiments were performed in a recirculating water channel and the mean flow in the upper layer was generated using a disk pump. A laser-Doppler velocimeter (with refractive-index matching) was used for velocity measurements and the techniques of laser-induced fluorescence (LIF) and plunging conductivity probes were used for concentration measurements. A number of turbulent length scales, and r.m.s. and mean velocity distributions in the upper mixed layer were measured. Images obtained using LIF were used to visualize the interfacial mixing events and to measure the thickness of the interfacial layer, the amplitude of the interfacial distortions, and the velocity fluctuations at the entrainment interface. The functional dependencies of measured parameters on the interfacial bulk Richardson number were also evaluated. © 1991, Taylor & Francis Group, LLC. All rights reserved.