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Numerical simulation of flowing suspensions in a channel: effect of non-inertial finite-size particles on the transition to turbulence.

Loisel, Vincent and Abbas, Micheline and Climent, Eric and Masbernat, Olivier Numerical simulation of flowing suspensions in a channel: effect of non-inertial finite-size particles on the transition to turbulence. (2012) In: 9th European Conference of Fluids Mechanics, 9 September 2012 - 13 September 2012 (Roma, Italy). (Unpublished)

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Abstract

Flows of concentrated suspensions (slurry flows) in ducts or channels are ubiquitous in industrial processes such as transport of mining extraction products, petroleum engineering, food industry, and others. The effects of particles on the carrying flow are not yet completely fully understood. In the case of non inertial particles (concentrated suspensions or emulsions), the hydrodynamic response of the flow is usually predicted using the concept of effective viscosity. However, recent experimental studies1,2 have shown that the transition to turbulence depends on the concentration and on the particle size in a non monotonous manner and this can not be scaled simply in terms of the mixture Reynolds number. This suggests the existence of some peculiar mechanisms which need to be investigated. These are essentially related to the two-phase nature of the flow: collective effects of particles, migration, hydrodynamic interactions ... The present work is based on direct numerical simulations of particulate flows in a straight channel (with periodic boundary conditions in the streamwise and spanwise directions). Flow equations are coupled to the force coupling method3 (FCM) to account for the dynamics of particles in the flow. Migration of isolated particles has been validated for a channel Poiseuille flow. Due to the competition between the shear induced lift force which causes the particles to migrate across streamlines, and the hydrodynamic interactions with the wall, particles tend towards an equilibrium position (similarly to the Segre-Silberberg effect). When the Reynolds number is increased, the equilibrium particle position moves closer to the wall. Results obtained for Reynolds numbers up to O(2000) and different particle-to-channel width ratios are in agreement with theoretical predictions based on matched asymptotic expansions4,5 . However in this range of Reynolds numbers, a channel flow is close to the transition to turbulence. Direct numerical simulations of single phase flow are used to characterise this regime, starting from a fully turbulent flow, and decreasing the Reynolds number progressively, until laminar flow occurs. In this work, the flow structure characterizing this transitional regime is described and the effect on the particle migration is discussed.

Item Type:Conference or Workshop Item (Lecture)
Audience (conference):International conference without published proceedings
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Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Institut National des Sciences Appliquées de Toulouse - INSA (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
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Deposited By: Eric CLIMENT
Deposited On:18 Dec 2013 07:41

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