The role of friction on size segregation of granular material

Abstract

The process of size segregation in a model system of granular matter, consisting of 1600 spherical polydis-perse particles stirred by a rectangular bar moving periodi-cally in the horizontal direction, was modelled by the dis-crete element method under different values of dynamic friction coefficient of the particle material. It has been shown that the dynamic friction coefficient influences the size segregation process in poly-disperse granular systems. The equation was proposed that characterises the evolution of segregation intensity approaching exponentially a cer-tain steady state value.The dependence of the rate of segregation inten-sity upon dynamic friction coefficient μ is nonmonoto-nous: the rate of segregation intensity is higher at lower values of the dynamic friction coefficient and attains a minimum value as the dynamic friction coefficient in-creases up to 10.≈μ, but starts to increase again for the higher values of the dynamic friction coefficient. This de-pendence indicates the presence of competing segregation mechanisms, one of which dominates at the given experi-mental conditions and material properties. The averaged velocity fields and flow lines demonstrate different pat-terns of collective flow of the granular matter at different values of dynamic friction.