Eur. Phys. J. B 6, 419-424 (1998)
https://doi.org/10.1007/s100510050569

Surface flows of granular mixtures: II. Segregation with grains of different size

Laboratoire de Physique de la Matière Condensée (URA 792 du CNRS) , Collège de France, 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France

Corresponding author: ^a boutreux.thomas@bcg.com

Received: 25 February 1998
Accepted: 6 July 1998
Published online: 15 December 1998

Abstract

We present the generalization of a theoretical model for segregation of granular mixtures due to surface flows, published in J. Phys. I France 6, 1295 (1996). Our generalized model is valid for grains differing by their size and/or their surface properties; in the present paper, we describe the case of two species with the same surface properties but two different sizes. The rolling stream is assumed to be homogeneous. Exchanges between the grains at rest and the rolling stream are modelized via binary collisions. The model predicts that during the filling of a two-dimensional silo, continuous segregation appears inside the static phase: small (respectively large) grains tend to stop uphill (respectively downhill), although both species remain present everywhere. This fits the observations when the size difference between the species is small. When the size difference is large, a different regime is observed. We argue that in this case, segregation occurs directly inside the rolling stream.