Eddy diffusivity of quasi-neutrally-buoyant inertial particles

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http://hdl.handle.net/10138/307126

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Afonso , M M , Muratore-Ginanneschi , P , Gama , S M A & Mazzino , A 2018 , ' Eddy diffusivity of quasi-neutrally-buoyant inertial particles ' , Physical Review Fluids , vol. 3 , no. 4 , 044501 . https://doi.org/10.1103/PhysRevFluids.3.044501

Title: Eddy diffusivity of quasi-neutrally-buoyant inertial particles
Author: Afonso, Marco Martins; Muratore-Ginanneschi, Paolo; Gama, Silvio M. A.; Mazzino, Andrea
Contributor: University of Helsinki, Department of Mathematics and Statistics
Date: 2018-04-04
Language: eng
Number of pages: 21
Belongs to series: Physical Review Fluids
ISSN: 2469-990X
URI: http://hdl.handle.net/10138/307126
Abstract: We investigate the large-scale transport properties of quasi-neutrally-buoyant inertial particles carried by incompressible zero-mean periodic or steady ergodic flows. We show howto compute large-scale indicators such as the inertial-particle terminal velocity and eddy diffusivity from first principles in a perturbative expansion around the limit of added-mass factor close to unity. Physically, this limit corresponds to the case where the mass density of the particles is constant and close in value to the mass density of the fluid, which is also constant. Our approach differs from the usual over-damped expansion inasmuch as we do not assume a separation of time scales between thermalization and small-scale convection effects. For a general flow in the class of incompressible zero-mean periodic velocity fields, we derive closed-form cell equations for the auxiliary quantities determining the terminal velocity and effective diffusivity. In the special case of parallel flows these equations admit explicit analytic solution. We use parallel flows to show that our approach sheds light onto the behavior of terminal velocity and effective diffusivity for Stokes numbers of the order of unity.
Subject: STRONG ANOMALOUS DIFFUSION
SCALAR TRANSPORT
TURBULENT-FLOW
BOUNDARY-LAYER
DISPERSION
EQUATIONS
SIMULATION
VELOCITY
FIELDS
SPHERE
114 Physical sciences
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