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Kinetic energy and enstrophy transfer in compressible Rayleigh–Taylor turbulence

Abstract Kinetic energy and enstrophy transfer in compressible Rayleigh–Taylor (RT) turbulence were investigated by means of direct numerical simulation. It is revealed that compressibility plays an important role in the kinetic energy and enstrophy transfer based on analyses of transport and large-scale equations. For the generation and transfer of kinetic energy, some findings have been obtained as follows. The pressure-dilatation work dominates the generation of kinetic energy in the early stage of flow evolution. The baropycnal work and deformation work handle the kinetic energy transfer from large to small scales on average for RT turbulence. The baropycnal work is mainly responsible for the kinetic energy transfer on large scales, and the deformation work for the kinetic energy transfer on small scales. The baropycnal work is also disclosed to be related to the compressibility from the finding that the expansion motion enhances the positive baropycnal work and the compression motion strengthens the negative baropycnal work. For the generation and transfer of enstrophy, the horizontal enstrophy is generated by the baroclinic effect and the vertical enstrophy by vortex stretching and tilting. Then the enstrophy is strengthened by the vortex stretching and tilting during the evolution of RT turbulence and the vorticity tends to be isotropic in the turbulent mixing region. The large-scale enstrophy equation in compressible flow has also been derived to deal with the enstrophy transfer. It is identified that the enstrophy is transferred from large to small scales on average and tends to stabilize for RT turbulence.