Understanding and exploiting competing segregation mechanisms in horizontally rotated granular media

Abstract

The axial segregation of granular and particulate media is a well-known but little-understood phenomenon with direct relevance to various natural and industrial processes. Over the past decades, many attempts have been made to understand this phenomenon, resulting in a significant number of proposed mechanisms, none of which can provide a full and universally applicable explanation. In this paper, we show that several mechanisms can be simultaneously active within a single system, and that by considering all relevant mechanisms, it is possible to understand and explain a system's segregative behaviours over a wider range of parameter space than is possible by considering any one, single process. We explore the interrelation and competition between the individual mechanisms present within a given system and demonstrate that by understanding these interactions, we can predict and even, through carefully designed systems, control their behaviour. In particular, we demonstrate that it is possible to deliberately direct segregation, allowing an arbitrary number of pre-determined segregation patterns to be induced in a system. We also illustrate a manner in which the competition between two opposing segregation mechanisms may be exploited in order to enhance the mixing of two dissimilar species of particle-a much sought after ability.

Comparing and contrasting size-based particle segregation models

“…During this process, smaller particles filter through the matrix of other particles, analogous to the gravity-driven void-filling mechanism, resulting in a net migration of small particles towards regions of lower fluctuation kinetic energy. Previously, Windows-Yule et al [50] experimentally investigated the competition between gravity-driven, kinetic-stress-driven, and other segregation mechanisms in axially non-uniform drums. Here, we consider a simpler scenario of size-bidisperse mixtures rapidly flowing down an inclined plane.…”

Positron Emission Particle Tracking for Liquid‐Solid Mixing in Stirred Tanks

“…(6) may be used on the resultant data to obtain a value for the ''overall'' homogeneity of the solids distribution. Finally, in addition to looking simply at the homogeneity of the particle distributions in absolute terms, one may also look at segregation between the different particle species using methodologies described in detail in [47,66,71].…”

Magnetic resonance imaging of granular materials

“…Even though X-ray CT is by far the strongest competitor, there are yet other imaging techniques useful for the study of granular materials. Positron Emission Tomography (PET) may provide information on segregation phenomena or other structural parameters of granular beds (see, e. g. [96]). In comparison with MRI, the PET sample preparation is more demanding, and PET also suffers from a limited selection of materials.…”