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Dispersion of particles from localized sources in turbulence

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We present a detailed investigation of particles relative separation in homogeneous isotropic turbulence. We use data from a 3D direct numerical simulations with 10243 collocation points and Rλ = 300 following the evolution of a large number of passive tracers and heavy inertial particles, with Stokes numbers in the range St ∈ [0.5,5]. Many studies [1, 2, 3] have focused on the subject, including extensions to the case of particles with inertia [4]. In particular, our simulation aims to investigate extreme events characterizing the distribution of relative dispersion in turbulent flows [5, 6]. To do that, we seed the flow with hundred millions of particles emitted from localized sources in time and in space. Thanks to such huge statistics, we are able to assess in a quantitative way deviations from Richardson’s prediction for tracers. Furthermore, we present the same kind of measures for heavy particles to understand how the inertia affects the pair separation statistics. Finally, to disentangle the effects of different turbulent scales, we present measurements based on exit time statistics for both tracer and inertial particles.

Author(s):

Riccardo Scatamacchia    
University of Tor Vergata
Italy

Luca Biferale    
University of Tor Vergata
Italy

Alessandra Sabina Lanotte    
ISAC CNR
Italy