To the Theory of Helical Turbulence of a Nonmagnetic Astrophysical Disk. Formation of Large-Scale Vortex Structures

Abstract

The paper presents a closed system of three-dimensional hydrodynamic equations of averaged motion, intended for modeling spiral turbulence in a rotating astrophysical disk. Diffusion equations for the averaged vortex and an equation for the transport of the integral vortex helicity are derived. A general concept of the emergence of energy-intensive mesoscale coherent vortex structures in a thermodynamically open turbulent chaos subsystem, associated with the realization of a reverse cascade of kinetic energy in mirror-asymmetrical disk turbulence, is formulated. It is shown that negative viscosity in a rotating three-dimensional disk system is apparently a manifestation of cascade processes in helical turbulence, when reverse energy transfer from small vortices to larger ones takes place. It is also shown that the relatively long decay of turbulence in the disk is associated with the lack of mirror symmetry of the anisotropic field of turbulent velocities about its equatorial plane. The work comprises a review aimed at improving new models of astrophysical nonmagnetic disks, for which the effects of helical turbulence play a decisive role.