Eur. Phys. J. E (2013) 36: 41
https://doi.org/10.1140/epje/i2013-13041-0

Regular Article

Spin Brazil-nut effect and its reverse in a rotating double-walled drum

¹⁹⁸⁵⁵ Department of Applied Physics, Nanjing University of Science and Technology, 210094, Nanjing, China
²⁹⁸⁵⁵ Department of Physics, University at Buffalo, State University of New York, 14260, New York, USA
³⁹⁸⁵⁵ School of Chemical Engineering, Nanjing University of Science and Technology, 210094, Nanjing, China

^* e-mail: hdc@njust.edu.cn
^** e-mail: sen@buffalo.edu

Received: 11 December 2012
Revised: 5 March 2013
Accepted: 26 March 2013
Published online: 23 April 2013

Abstract

The segregation of binary mixtures in a filled rotating double-walled drum is explored by simulations. Based on the characteristics of self-gravity and the centrifugal force, we argue that both percolation and buoyancy effects dominate the segregation process. The simulational results show that up to long enough times the segregation state is controlled by the rotational speed, the particle radius and density. At low rotational speeds, the smaller and heavier particles tend to accumulate towards the inner drum wall and the bigger and lighter ones towards the outer drum wall, while the segregation pattern reverses completely at higher rotational speeds. Two typical phase diagrams in the space of the density and radius ratio of bigger particles to smaller particles further confirm the predictions.