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Experimental study of the sedimentation of dilute and semi-dilute suspensions of fibres

Published online by Cambridge University Press:  10 April 1999

BENJAMIN HERZHAFT  and
ÉLISABETH GUAZZELLI
BENJAMIN HERZHAFT
Affiliation:
Laboratoire de Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 10 rue Vauquelin, 75231 Paris CEDEX 05, France Present address: Institut Français du Pétrole, 1–4 Avenue de Bois-Préau, BP311, 92506 Rueil-Malmaison Cedex, France.
ÉLISABETH GUAZZELLI
Affiliation:
Laboratoire de Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, ESPCI, 10 rue Vauquelin, 75231 Paris CEDEX 05, France Present address: Institut Universitaire des Systèmes Thermiques Industriels, UMR 6595 du CNRS, Technopôle de Château-Gombert, 5 rue Enrico Fermi, 13453 Marseille Cedex 13, France.
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Abstract

Steady-state velocity and orientation distributions of sedimenting fibres were measured as a function of particle concentration and aspect ratio. Two different regimes of sedimentation were clearly identified. For dilute suspensions, the fibres tend to align in the direction of gravity with occasional flipping and clump together to form packets. In this regime, the vertical mean sedimentation speed is not hindered and can be larger than the Stokes' velocity of an isolated vertical fibre. Its scaling is a complex function of particle volume fraction and aspect ratio. As the concentration is increased, the fibres still tend to orient in the direction of gravity. The mean velocity becomes hindered and scales with particle volume fraction. The velocity fluctuations were found to be large and anisotropic. They were found to increase with increasing volume fraction. A similar substantial anisotropy of the orientation distribution was observed for all particle concentrations and aspect ratios studied.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 384 , 10 April 1999 , pp. 133 - 158
Copyright
© 1999 Cambridge University Press

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