Cohesion-driven mixing and segregation of dry granular media

Abstract

Granular segregation is a common, yet still puzzling, phenomenon encountered in many natural and engineering processes. Here, we experimentally investigate the effect of particles cohesion on segregation in dry monodisperse and bidisperse systems using a rotating drum mixer. Chemical silanization, glass surface functionalization via a Silane coupling agent, is used to produce cohesive dry glass particles. The cohesive force between the particles is controlled by varying the reaction duration of the silanization process, and is measured using an in-house device specifically designed for this study. The effects of the cohesive force on flow and segregation are then explored and discussed. For monosized particulate systems, while cohesionless particles perfectly mix when tumbled, highly cohesive particles segregate. For bidisperse mixtures of particles, an adequate cohesion-tuning reduces segregation and enhances mixing. Based on these results, a simple scheme is proposed to describe the system’s mixing behaviour with important implications for the control of segregation or mixing in particulate industrial processes.

Efficacy of simple continuum models for diverse granular intrusions

“…Drag and lift forces on submerged objects in granular media are relevant in processes such as mixing, mining, soil-buried pipelines, and animal locomotion [39][40][41] . Over the past two decades, several studies [42][43][44][45] have explored the mechanisms and the variation of these forces by considering the horizontal dragging of submerged, rigid cylinders (at different depths) as a test case.…”

Cohesion-controlled granular material

“…Despite a good knowledge of the cohesion force arising from capillary bridges [22] the bulk behavior and the rheological measurements suggest a complex dynamics due to the evolution of the capillary bridges during shear, which may migrate and coalesce [23,24]. Recently [25], silanization has been used to modify the surface properties of glass particles and build a cohesive force of 0.1 mN order of magnitude. Experimental research on cohesive materials would strongly benefit from a model system making it possible to tune at will, and through a simple process, the cohesion between the grains.…”

Toward general regime maps for cohesive‐particle flows: Force versus energy‐based descriptions and relevant dimensionless groups

“…A long‐standing point of debate in cohesive‐particle systems is whether a force‐based or energy‐based description of particle interactions is more appropriate. Estimates of agglomerate size, 19,55–57 constitutive relations for source terms in populations balances, 24,58–63 and regime maps 15,26,62,64–69 are a few prominent examples in which both force‐ and energy‐based descriptions have appeared in the literature, without justification as to why one is more appropriate than the other. Here we aim to decipher the force versus energy conundrum.…”