Density-Driven Segregation in Binary and Ternary Granular Systems

Windows-Yule, Kit; Parker, David J.

doi:10.14356/kona.2015004

Cited by 23 publications

(9 citation statements)

References 32 publications

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“…For systems in a non-equilibrium steady state (NESS), the motion of the single tracer particle used can be utilized to extract various important parameters pertaining to the dynamics of the system as a whole [42]. The quantities which may be obtained using PEPT include, but are by no means limited to, packing densities [42], granular temperatures [43] and velocities [44], as well as the spatial distributions thereof, mean squared displacement and diffusive behaviours [45] and even segregation in binary [46] and polydisperse systems [47]. In the current paper, however, we are predominantly concerned with our systems' time-averaged vertical centre of mass positions, h, which provide an accurate measure of the mean gravitational potential energy (E P ) possessed by a granular bed.…”

Section: Data Acquisition-positron Emission Particle Tracking (Pept)mentioning

confidence: 99%

Resonance effects on the dynamics of dense granular beds: achieving optimal energy transfer in vibrated granular systems

et al. 2015

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Using a combination of experimental techniques and discrete particle method simulations, we investigate the resonant behaviour of a dense, vibrated granular system. We demonstrate that a bed of particles driven by a vibrating plate may exhibit marked differences in its internal energy dependent on the specific frequency at which it is driven, even if the energy corresponding to the oscillations driving the system is held constant and the acceleration provided by the base remains consistently significantly higher than the gravitational acceleration, g. We show that these differences in the efficiency of energy transfer to the granular system can be explained by the existence of resonances between the bed's bulk motion and that of the oscillating plate driving the system. We systematically study the dependency of the observed resonant behaviour on the system's main, controllable parameters and, based on the results obtained, propose a simple empirical model capable of determining, for a given system, the points in parameter space for which optimal energy transfer may be achieved. been demonstrated [15] that, for relatively shallow, strongly fluidized systems, this assumption does not necessarily hold true; rather, the dynamic properties of a vertically vibrated granulate are additionally sensitive to the specific combinations of f and A used to produce a given v, S or Γ. In other words, two systems vibrated with the same input energy achieved using two differing combinations of f and A may exhibit strongly disparate properties. Similarly, it is found that two systems driven with markedly different S and/or Γ values may possess near-identical internal energies, in direct contradiction of the monotonic relations one might expect.Specifically, for dilute systems such as those described in [15], it was found that an increase in A at fixed S resulted in an increase in the total energy possessed by the excited granulate. This greater energy transfer from the vibrating system to the granular bed at large driving amplitudes was attributed to the observed increase in the particle-base collision rate with increasing A. In other words, the lack of a simple, monotonic relationship between a granulate's kinetic and/or potential energy and any of the individual parameters v S , or Γ can be explained by the fact that such parameters do not provide sufficient information regarding certain key variables, in this case the particle-base collision rate within the system. As such, in order to accurately characterize the steady-state of such a system, one requires a pair of driving variables, f and A-in addition, of course, to a knowledge of the system's depth and dissipative properties.Recent works by Pugnaloni et al [16,17] have similarly challenged the assumption that a system's steady state may be adequately defined by a single parameter, in this instance for the case of a granular bed excited by a series of discrete taps, as opposed to continuous vibration. Specifically, it was, until recently, a generally held belief [18,19] that ...

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Section: Data Acquisition-positron Emission Particle Tracking (Pept)mentioning

confidence: 99%

Resonance effects on the dynamics of dense granular beds: achieving optimal energy transfer in vibrated granular systems

et al. 2015

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“…To ensure a steady state, the acquisition of each data set is preceded by a period of 1000 s during which the system is excited, but no data are recorded. For the systems investigated here, this period should be more than adequate to allow a steady state to be achieved [43,44], The steady state of all systems is confirmed by subdividing each data set into a series of overlapping 200 s segments and ensuring consistency in i){z) between each segment. For additional information regarding PEPT and its applicability to monodisperse and bidisperse systems, please refer to Refs.…”

Section: Nf(z)d3mentioning

confidence: 99%

Competition between geometrically induced and density-driven segregation mechanisms in vibrofluidized granular systems

2015

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The behaviors of granular systems are sensitive to a wide variety of particle properties, including size, density, elasticity, and shape. Differences in any of these properties between particles in a granular mixture may lead to segregation, or "demixing," a process of great industrial relevance. Despite the known influence of particle geometry in granular systems, a considerable fraction of research into these systems concerns only uniformly spherical particles. We address, for the case of vertically vibrated granular systems, the important question of whether the introduction of differing particle geometries entirely invalidates our existing knowledge based on purely spherical granulates, or whether current models may simply be adapted to account for the effects of particle shape. We demonstrate that while shape effects can indeed influence the dynamical and segregative behaviors of a granular system, the segregative mechanisms associated with particle geometry are decidedly secondary to those related to particle density. The relevant control parameters determining the extent of geometrically induced segregation are established. Finally, a manner in which shape effects may be accounted for in simulations utilizing purely spherical particles is proposed.

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“…Although PEPT tracks a single particle, for systems in a steady state the principle of ergodicity allows the extraction of data pertaining to the system as a whole through appropriate time-averages, as shown in detail in our reference [70]. Indeed, PEPT has been successfully used to determine steady-state density and temperature distributions [73], velocity fields [74,75] and segregation patterns [76] as well as numerous additional important, whole-field quantities in a diverse range of systems [77][78][79]. In order to obtain useful data from binary systems such as ours, it is simply necessary to repeat every experiment using a tracer of each species, combining the time-averaged data from each separate run [80].…”

Section: Data Acquisition-positron Emission Particle Trackingmentioning

confidence: 99%

Understanding and exploiting competing segregation mechanisms in horizontally rotated granular media

et al. 2016

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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.

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Density-Driven Segregation in Binary and Ternary Granular Systems

Cited by 23 publications

References 32 publications

Resonance effects on the dynamics of dense granular beds: achieving optimal energy transfer in vibrated granular systems

Resonance effects on the dynamics of dense granular beds: achieving optimal energy transfer in vibrated granular systems

Competition between geometrically induced and density-driven segregation mechanisms in vibrofluidized granular systems

Understanding and exploiting competing segregation mechanisms in horizontally rotated granular media

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