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Collision rate for suspensions at large Stokes numbers - comparing Navier-Stokes and synthetic turbulence

Voßkuhle, Michel; Pumir, Alain; Lévêque, Emmanuel and Wilkinson, Michael (2014). Collision rate for suspensions at large Stokes numbers - comparing Navier-Stokes and synthetic turbulence. Journal of Turbulence, 16(1) pp. 15–25.

DOI (Digital Object Identifier) Link: https://doi.org/10.1080/14685248.2014.948628
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Abstract

The use of simplified models of turbulent flows provides an appealing possibility to study the collision rate of turbulent suspensions, especially in conditions relevant to astrophysics, which require large timescale separations. To check the validity of such approaches, we used a direct numerical simulation (DNS) velocity field, which satisfies the Navier–Stokes equations (although it neglects the effect of the suspended particles on the flow field), and a kinematic simulation (KS) velocity field, which is a random field designed so that its statistics are in accord with the Kolmogorov theory for fully-developed turbulence. In the limit where the effects of particle inertia (characterised by the Stokes number) are negligible, the collision rates from the two approaches agree. As the Stokes number St increases, however, we show that the DNS collision rate exceeds the KS collision rate by orders of magnitude. We propose an explanation for this phenomenon and explore its consequences. We discuss the collision rate R for particles in high Reynolds number flows at large Stokes number, and present evidence that R α √St.

Item Type: Journal Item
Copyright Holders: 2014 Taylor & Francis
ISSN: 1468-5248
Keywords: collisions; kinematic simulation; caustics; planet formation; rainfall
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Mathematics and Statistics
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 41303
Depositing User: Michael Wilkinson
Date Deposited: 13 Nov 2014 10:49
Last Modified: 07 Dec 2018 10:26
URI: http://oro.open.ac.uk/id/eprint/41303
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