PREDICTIONS OF SMALL-SCALE STATISTICS FOR A PASSIVE SCALAR IN TURBULENT MIXING

This Letter presents some quantitative predictions for the small-scale statistics for a passive scalar mixed in a fully turbulent flow. Our method uses an equation [S. Vaienti et al. Physica (Amsterdam) 73D, 99 (1994)] which controls the evolution through the scales of the probab ility density function of temperature increments. This equation, which needs some closure as well as initial data, uses results from direct numerical simulations or from experiments. For the dissipative and sma ll inertial range scales, our predictions are in excellent agreement w ith the measured or numerically calculated probability density functio ns. The associated Yaglom equation is also well verified for the same range of scales.