  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.
