Nonlocal Turbulent Diffusion Models

Large time behavior of nonlocal aggregation models with nonlinear diffusion

The aim of this paper is to establish rigorous results on the large time behavior of nonlocal models for aggregation, including the possible presence of nonlinear diffusion terms modeling local repulsions. We show that, as expected from the practical motivation as well as from numerical simulations, one obtains concentrated densities (Dirac δ distributions) as stationary solutions and large tim...

A closed form solution for pollutant dispersion in atmosphere considering nonlocal closure of the turbulent diffusion

Atmospheric air pollution turbulent fluxes can be assumed proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection-diffusion equation. Moreover, large eddies are able to mix scalar quantities in a manner that is counter to the local gradient. In this work we present an analytical solution of the three-dimensional steady stat...

Subgrid models for mass and thermal diffusion in turbulent mixing∗

Intermittency in Turbulent Diffusion Models with a Mean Gradient

This paper provides a rigorous, self contained analysis of the intermittent behavior of turbulent diffusion models with a mean gradient. The intermittency can be described as large spikes randomly occurring in the time sequence of a passive tracer or exponential like fat tails in the probability density function. This type of passive tracer intermittency is subtle and occurs without any positiv...

Turbulent pair diffusion.

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...