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Soft Matter and Biological Physics

Eur. Phys. J. E 1, 105-114

Settling and fluidization of non Brownian hard spheres in a viscous liquid

P. Snabre1 - P. Mills2

1 Institut de Science et de Génie des Matériaux et Procédés, B.P. 5, 66125 Font-Romeu, France
2 L.P.M.D.I, Université de Marne-la-Vallée, 5 boulevard Descartes, Champs-sur-Marne, 77454 Marne-la-Vallée Cedex, France
snabre@imp-odeillo.fr

Received 22 February 1999 and Received in final form 14 June 1999

Abstract
A mean field approach is used to estimate the energy dissipation during the homogeneous sedimentation or the particulate fluidization of non Brownian hard spheres in a concentrated suspension of infinite extent. Depending on inertial screening and the range of the hydrodynamic interactions, the effective buoyancy force is determined either from the average suspension density in a Stokes flow or from the fluid density in the turbulent flow regime. An energy balance then yields a settling or fluidization law depending on the particle Reynolds number in reasonable agreement with the Richardson and Zaki correlation and recent experimental results for particle settling or fluidization. We further estimate the energy dissipation in the turbulent boundary layers around the particles to precise the Reynolds number dependence of the hindered settling function in the intermediate flow regime.

PACS
47.55.Kf Multiplase and particle-laden flows - 47.90.+a Other topics in fluid dynamics - 83.10.Lk Multiplase flows

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