Abstract

During a typical silo discharge, the material flow rate is determined by the contact forces between the grains. Here, we report an original study concerning the discharge of a two-dimensional silo filled with repelling magnetic grains. This non-contact interaction leads to a different dynamics from the one observed with conventional granular materials. We found that, although the flow rate dependence on the aperture size follows roughly the power-law with an exponent 3/2 found in non-repulsive systems, the density and velocity profiles during the discharge are totally different. New phenomena must be taken into account. Despite the absence of contacts, clogging and intermittence were also observed for apertures smaller than a critical size determined by the effective radius of the repulsive grains. Received: 10 July 2015, Accepted: 7 August 2015; Edited by: L. A. Pugnaloni; Reviewed by: J. R. Darias, Universidad Simón o Bolívar, Caracas, Venezuela; DOI: http://dx.doi.org/10.4279/PIP.070013Cite as: G Lumay, J Schockmel, D Henández-Enríquez, S Dorbolo, N Vandewalle, F Pacheco-Vázquez, Papers in Physics 7, 070013 (2015)This paper, by G Lumay, J Schockmel, D Henández-Enríquez, S Dorbolo, N Vandewalle, F Pacheco-Vázquez, is licensed under the Creative Commons Attribution License 3.0.

Highlights

  • The flow of discrete objects through an aperture in bottlenecks is an important subject in many scientific fields and for industrial applications

  • The flow rate dependence on the aperture size follows roughly the power-law with an exponent 3/2 found in non-repulsive systems, the density and velocity profiles during the discharge are totally different

  • Beverloo proposed a semi-empirical relation for the granular flow rate Q at the output of a silo as a function of the silo aperture size D

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Summary

Introduction

The flow of discrete objects through an aperture in bottlenecks is an important subject in many scientific fields and for industrial applications. Beverloo proposed a semi-empirical relation for the granular flow rate Q (number of grains per unit time) at the output of a silo as a function of the silo aperture size D. For the average grains speed at the silo output, one has vout = 2gβD This relation comes from the idea that the jamming mechanism is due to the formation of a semicircular arch before the aperture [12, 15]. Where μ0 is the vacuum magnetic permittivity and m is the dipolar magnetic moment The influence of this magnetic interaction on the flow of dense granular materials has been already considered in a previous study [20]. The nonlinear repulsive force strength between two grains in the silo is Considering this repulsive interaction, we investigate the flow rate at the silo output for different aperture sizes. The relations between the flow rate, the velocity profile along the silo aperture and the density behind the aperture are investigated

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