Eur. Phys. J. E 9, 55-62 (2002)
DOI: 10.1140/epje/i2002-10054-8

Aggregation of particles settling in shear-thinning fluids

Part 2. Three-particle aggregation

S. Daugan^{1, 2}, L. Talini¹, B. Herzhaft² and C. Allain<sup>1

1</sup>  Laboratoire FAST, Bât. 502, Campus Universitaire, 91405 Orsay Cedex, France
²  Institut Français du Pétrole, 1 et 4 avenue de Bois Préau, 92852 Rueil Malmaison, France

talini@fast.u-psud.fr

(Received 10 July 2002 / Published online: 7 November 2002)

Abstract
We have experimentally studied the coaxial settling of three identical non-Brownian spheres in a shear-thinning fluid at small Reynolds numbers. While settling, the particles create corridors of reduced viscosity in their wake and, if they are initially close enough to one another, they can form stable clusters. By analogy with previous results obtained on two-particle interaction in the first part of this work, we show that the particle velocities can be satisfactorily described using a first-order expression and assuming that the reduced viscosity remains constant. We report systematic experiments performed at different initial separation distances between particles and the use of our simple model allows the prediction of the settling behaviour and in particular the conditions for clusters formation. We thus show that particle aggregation can occur even for large initial distances between particles and within times that are small compared to the time scales in Newtonian fluids.

PACS
47.15.Gf - Low-Reynolds-number (creeping) flows.
82.70.Kj - Emulsions and suspensions.
47.50.+d - Non-Newtonian fluid flows.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002