The statistical properties of the kinetic epsilon(u) and thermal epsilon(theta) energy dissipation rates in two-dimensional Rayleigh-Taylor (RT) turbulence are studied by means of direct numerical simulations at small Atwood number and unit Prandtl number. Although epsilon(theta) is important but epsilon(u) can be neglected in the energy transport processes, the probability density functions of epsilon(u) and epsilon(theta) both show self-similarity properties during the RT evolution. The distributions are well fitted by a stretched exponential function and found to depart distinctly from the log-normal distribution for small amplitudes. Within the turbulent range, the intense dissipation events occur near the interfaces of hot and cold fluids, leading to a strong positive correlation between epsilon(u) and epsilon(theta). Our results further reveal that although there is no constant fractal dimension for the fluid interfaces within the inertial range, the local fractal dimensions obtained at different times share similar scale-dependence. Published by AIP Publishing.
展开▼
