Mixing characteristics in buoyancy-driven, variable density turbulence

Abstract

We examine the mixing induced by buoyancy generated motions in ar unstably stratified field composed of two incompressible miscible fluids with different densities, as occurs in variable density Rayleigh-Taylor instability. The statistically homogeneous case is considered as a unit problem for variable density turbulence. It involves both the transition to turbulence and the decay of turbulence as the friction forces overcome buoyancy generation. Diverse mixing metrics and their dependence on the Atwood, Reynolds, and Schmidt numbers are used to study the homogeniza-tion of the two fluids leading to the subsequent reduction of the net buoyancy force and the turbulence generation mechanism.