DYNAMICS OF THE PASSIVE SCALAR IN COMPRESSIBLE TURBULENT-FLOW - LARGE-SCALE PATTERNS AND SMALL-SCALE FLUCTUATIONS

The work analyzes fluctuations of passive scalar and large-scale (mean field) effects in a turbulent compressible fluid how. It is shown that passive scalar transport can be accompanied by slow diffusion of small-scale inhomogeneous fluctuating structures for large Peclet numbers, Pe much greater than 1. The origin of the inhibition of the diffusion of small-scale fluctuations of the passive scalar is associated with compressibility (i.e., div u proportional to partial derivative rho/partial derivative t not equal 0) of a surrounding fluid how. The conditions for the slow diffusion of the passive scalar fluctuations in homogeneous and isotropic turbulent how are found. It is shown that the magnitude of the fluctuations of the passive scalar generated in the presence of external gradient of the mean mass; concentration del Q in compressible fluid how can be fairly strong: root(q(2))similar to l(o)In(Pe)\del Q\, where l(0) is the characteristic scale of the turbulent velocity field. The characteristic spatial scale of a localization of solutions is of the order of l(0)/root Pe. In addition, compressibility in the stratified turbulent inhomogeneous fluid how [i.e., div u = -(V rho . u)/rho not equal 0] results information of large-scale structures for large P6clet numbers. The formation of these patterns is caused by the instability of the uniform distribution of the mean passive scalar held whereby an additional nondiffusive component of the flux of passive scalar particles results in a large-scale pattern. The conditions for the excitation of the instability of the mean held are found. Possible environmental applications of these effects are discussed.