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Transport and mixing in Rayleigh-Taylor turbulence
The Rayleigh-Taylor (RT) instability is a fluid-mixing mechanism arising at the interface between two fluids of different density when the heavy, denser, fluid is accelerated into the lighter one. The reduction of fluid potential energy drives the growth of a perturbation along the interface to form a mixing region whose width grows in time. At sufficiently long time, the fluid motions in the mixing zone become turbulent. The relevance of this mixing mechanism embraces several phenomena occurring in different contexts : astrophysical supernovae and solar-flare development are some examples. A deeper understanding of the mechanism of flows driven by RT instability would thus shed light on the many processes that underpin fully developed turbulence. Along this direction, we performed direct numerical simulations in order to investigate the statistical properties of turbulent mixing. An introduction to this instability will be provided and some of our numerical results will be discussed.