Loisel, Vincent and Abbas, Micheline and Masbernat, Olivier and Climent, Éric Dynamics of laminar pressuredriven channel flows laden with neutrally buoyant finitesize particles. (2013) In: Euromech Colloquium 555 : Smallscale numerical methods for multiphase flows, 28 August 2013  30 August 2013 (Bordeaux, France). (Unpublished)

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Abstract
Since the pioneering work of Reynolds (1883), much effort has been allocated on the topic of laminarturbulent transition regime in a singlephase flow, with special focusing on the unstable and intermittent natures of this regime (Mullin, 2011). The transition regime of dispersed flows carried less attention even though dispersed flows are used in many industrial processes. As for suspensions of neutrally buoyant particles, Matas et al. (2003) observed changes in the values of the critical Reynolds numbers depending on both the solid volume fraction and the particletopipe sizeratio. Typically, the transition occurs at lower Reynolds numbers when the flow carries macrosized particles at dilute to moderate concentrations (up to 25%). On the contrary, the critical Reynolds numbers of the onset of transition is shifted towards greater values when particles are microsized and their concentration is higher. In this work, we aim at understanding the mechanisms lying behind the shift of the laminarturbulent transition regime down to lower critical Reynolds numbers in suspension flows of macrosized particles. Fullycoupled numerical simulations are used to investigate the interactions between neutrallybuoyant finitesize particles and a transitional channel flow. To our knowledge, other than the simulations of Shao et al. (2012) and GarciaVillalba et al. (2012) performed in turbulent channel flows, there are no direct numerical simulations performed on fluctuating suspension flows in channels or pipes with finitesize particles. The numerical method chosen for this work is the ForceCoupling Method (FCM) (Maxey and Patel, 2001, Lomholt and Maxey 2003). It is fullyresolved in the sense that the fluid equations are solved at a lengthscale smaller than the particle radius. In a first step, the laminarization process of a singlephase flow initially turbulent at Re=6000 is statistically characterized (Re is based on the average flow velocity, the channel height and the kinematic viscosity). In a second step, particles are randomly added to the fluctuating channel flow at a solid volume fraction of 5%, the size ratio of particle diameter to channel height being 1/16. The starting point of the calculation of the suspension flow is a snapshot taken from the singlephase flow case at Re=1625 (the smallest Reynolds number at which the flow does not relaminarize).
Item Type:  Conference or Workshop Item (Paper) 

Audience (conference):  International conference 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:  16 Dec 2013 10:36 
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