# Variable-density buoyancy-driven turbulence with asymmetric initial density distribution

## TL;DR

This study investigates how asymmetric initial density distributions influence buoyancy-driven turbulence at different Atwood numbers using high-resolution simulations, revealing significant effects at high Atwood numbers but limited impact at low Atwood numbers.

## Contribution

It provides new insights into the effects of initial density asymmetry on turbulence evolution in variable-density flows at different Atwood numbers.

## Key findings

- At high Atwood numbers, initial asymmetry significantly affects flow evolution.
- At low Atwood numbers, initial asymmetry has limited impact on flow dynamics.
- Late-time flow parameters become independent of initial composition ratio after full mixing.

## Abstract

The effects of different initial density distributions on the evolution of buoyancy-driven homogeneous variable-density turbulence (HVDT) at low (0.05) and high (0.75) Atwood numbers are studied by using high-resolution direct numerical simulations. HVDT aims to mimic the acceleration-driven Rayleigh-Taylor and shock-driven Richtmyer-Meshkov instabilities and reveals new physics that arise from variable-density effects on the turbulent mixing. Here, the initial amounts of pure light and pure heavy flows are altered primarily to mimic the variable-density turbulence at the different locations of the Rayleigh-Taylor and Richtmyer-Meshkov instabilities' mixing layers where the amounts of the mixing fluids are not equal. It is found that for the low Atwood number cases, the asymmetric initial density distribution has limited effects on both global and local flow evolution for HVDT. However, at high Atwood number, both global flow evolution and the local flow structures are strongly affected by the initial composition ratio. The flow composed of more light fluid reaches higher turbulent levels and the local statistics reach their fully-developed behavior earlier in the time evolution. During the late time decay, where most of the flow is well-mixed, all parameters become independent of the initial composition ratio for both low and high Atwood number cases.