1 research outputs found
Reactive Rayleigh-Taylor Turbulence
The Rayleigh-Taylor (RT) instability develops and leads to turbulence when a
heavy fluid falls under the action of gravity through a light one. We consider
this phenomenon accompanied by a reactive transformation between the fluids,
and study with Direct Numerical Simulations (DNS) how the reaction (flame)
affects the turbulent mixing in the Boussinesq approximation. We discuss "slow"
reactions where the characteristic reaction time exceeds the temporal scale of
the RT instability. In the early turbulent stage, effects of the flame are
distributed over a maturing mixing zone, whose development is weakly influenced
by the reaction. At later times, the fully mixed zone transforms into a
conglomerate of pure-fluid patches of sizes proportional to the mixing zone
width. In this "stirred flame'' regime, temperature fluctuations are consumed
by reactions in the regions separating the pure-fluid patches. This DNS-based
qualitative description is followed by a phenomenology suggesting that thin
turbulent flame is of a single-fractal character, and thus distribution of the
temperature field is strongly intermittent.Comment: 14 pages, 4 figure