Scale to scale energy and enstrophy transport in two dimensional Rayleigh Taylor turbulence
We apply a recently developed filtering approach, i.e. filter space technique (FST) to study the scale to scale transport of kinetic energy, thermal energy, and enstrophy in two dimensional (2D) Rayleigh Taylor (RT) turbulence. Although the scaling laws of the energy cascades in 2D RT systems follow the Bolgiano Obukhov (BO59) scenario due to buoyancy forces, the kinetic energy is still found to be, on average, dynamically transferred to large scales by an inverse cascade, while both the mean thermal energy and the mean enstrophy move towards small scales by forward cascades. In particular, there is a reasonably extended range over which the transfer rate of thermal energy is scale independent and equals the corresponding thermal dissipation rate at different times. This range functions similarly to the inertial range for the kinetic energy in the homogeneous and isotropic turbulence. Our results further show that at small scales the fluctuations of the three instantaneous local fluxes are highly asymmetrically distributed and there is a strong correlation between any two fluxes. These small scale features are signatures of the mixing and dissipation of fluids with steep temperature gradients at the fluid interfaces.
Journal of Fluid Mechanics