Visualizations of Buoyancy Driven Mixing

A collection of visualizations that convey a basic understanding of buoyancy-driven mixing is presented. Buoyancy-driven mixing resulting from the Rayleigh-Taylor instability occurs in a unstably stratified flow when a heavy fluid rests above a light fluid. The difficulty of creating an unstable density stratification and repeatable fluid interface has made studying the Rayleigh-Taylor instability a challenging task. Our experiments utilize a water channel and most recently a gas channel (low speed wind tunnel). The experimental configuration allows unstable perturbations to develop into a mixing layer as they travel downstream. Thus resulting in a repeatable experiment and statistically steady flow. Various visualization techniques have been used to observe the development of the Rayleigh-Taylor instability. Visualizations using Nigrosene dye as a fluid marker are shown in the evolution of single and binary mode perturbations due to the Rayleigh-Taylor instability. In contrast, visualizations of the Rayleigh-Taylor instability developed from multi-mode perturbations are seen for the gas channel using both fog and smoke to visualize the flow. Together these techniques help provide an understanding for the nature and complexity of buoyancy driven mixing. Copyright © 2005 by ASME