DOI: 10.1209/epl/i2003-00287-1
Europhys. Lett., 64 (2) , pp. 190-196 (2003)

Segregation in a fluidized binary granular mixture: Competition between buoyancy and geometric forces

L. Trujillo¹, M. Alam^{2, 3} and H. J. Herrmann<sup>1, 2

1</sup>  PMMH (UMR CNRS 7636), ESPCI - 10 rue Vauquelin, 75231 Paris Cedex 05, France
²  Institut für Computeranwendungen 1, Pfaffenwaldring 27 D-70569 Stuttgart, Germany
³  Engineering Mechanics Unit, Jawaharlal Nehru Center for Advanced Scientific Research Jakkur Campus, Bangalore 560064, India

meheboob@jncasr.ac.in

(Received 23 June 2003; accepted in final form 8 August 2003)

Abstract
Starting from hydrodynamic equations of binary granular mixtures, we derive an evolution equation for the relative velocity of the intruders, which is shown to be coupled to the inertia of the smaller particles. The onset of Brazil nut segregation is explained as a competition between the buoyancy and geometric forces: the Archimedean buoyancy force, a buoyancy force due to the difference between the energies of two granular species, and two geometric forces, one compressive and the other one tensile in nature, due to the size difference. We show that inelastic dissipation strongly affects the phase diagram of the Brazil nut phenomenon and our model is able to explain the experimental results of Breu et al.  (Phys. Rev. Lett. 90 (2003) 014302).

PACS
45.70.Mg - Granular flow: mixing, segregation and stratification.
05.20.Dd - Kinetic theory.

© EDP Sciences 2003