Effective diffusion and dispersion of inertial particles in flowing fluids

We perform an analytical study of the inertial-particle dynamics in the limit of small but finite inertia, in incompressible flows, exploring two specific issues. First, by means of a multiscale expansion, we analyse the particle effective diffusivity, and in particular its dependence on Brownian diffusivity, gravity and particle-to-fluid density ratio. We identify some cases of anomalous diffusion. Secondly, we investigate the concentration of particles continuously emitted from a point source with a given exit velocity distribution. The anisotropy of the latter turns out to be a necessary factor for the presence of a correction (with respect to the corresponding tracer case) at order square root of the Stokes number. In both cases, we obtain forced advection-diffusion equations for auxiliary quantities in the physical space, thus simplifying the problem from the full phase space to a system which can easily be solved numerically. Copyright © ETC 2013 - 14th European Turbulence Conference.All rights reserved.Non peer reviewe