We studied experimentally a new phenomenon of turbulent thermal diffusion of particles which can cause formation of the large-scale aerosol layers in the vicinity of the atmospheric temperature inversions. This phenomenon was detected experimentally in oscillating grids turbulence in air flow. Three measurement techniques were used to study turbulent thermal diffusion in strongly inhomogeneous ...

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A model is considered for turbulent diffusion which consists of a Riesz space fractional derivative to describe the turbulent phenomenon and also includes advection and classical diffusion. We present a first order explicit numerical method and a second order implicit numerical method to solve our problem and prove convergence results for both methods, including the derivation of stability cons...

A brief review of the emergence and development nonlocal approach to problem turbulent diffusion with a discussion physical reasons nonlocality is given. The main attention paid fractional differential operators. In concluding paper, author’s original results on applications cosmic rays in interstellar galactic medium are presented.

We investigate the question of whether ambipolar diffusion (ion-neutral drift) determines the smallest length and mass scale on which structure forms in a turbulent molecular cloud. We simulate magnetized turbulence in a mostly neutral, uniformly driven, turbulent medium, using a three-dimensional, two-fluid, magnetohydrodynamics (MHD) code modified from Zeus-MP. We find that substantial struct...

We use direct numerical simulations to compute turbulent transport coefficients for passive scalars in turbulent rotating flows. Effective diffusion coefficients in the directions parallel and perpendicular to the rotation axis are obtained by studying the diffusion of an imposed initial profile for the passive scalar, and calculated by measuring the scalar average concentration and average spa...

Kinematic simulations of turbulent pair diffusion in planar turbulence with a k(-5/3) energy spectrum reproduce the laboratory results of Jullien et al. [Phys. Rev. Lett. 82, 2872 (1999)]], in particular the stretched exponential form of the probability density function of pair separations and their correlation functions. The root mean square separation is found to be strongly dependent on init...

where 2S is the viscosity computed by the Smagorinsky formulation (Smagorinsky, 1963), α is a constant in the range 0.01-0.5 and A denotes the area of the current element. A value of α = 0.1 was used keeping in mind the fine resolution of the mesh. Similar to the eddy viscosity, turbulent diffusion in the transport equations (equation 4 in the paper) represents all those processes that can not ...