Granular discharge rate for submerged hoppers

Wilson, Timothy L.; Pfeifer, Charlotte R.; Mesyngier, N.; Durian, Douglas J.

doi:10.4279/pip.060009

Cited by 39 publications

(62 citation statements)

References 34 publications

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“…In both dry and submerged cases, the grain volume fraction is measured to be φ = 0.58 ± 0.04, which is close to expectation [31]. Therefore, the mass density of the packing is ρ = φρ g = 1.47 ± 0.10 g/cm 3 . The draining angle of repose is about 24…”

Section: Methodssupporting

confidence: 68%

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Effect of interstitial fluid on the fraction of flow microstates that precede clogging in granular hoppers

Koivisto

Durian

2017

Phys. Rev. E

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We report on the nature of flow events for the gravity-driven discharge of glass beads through a hole that is small enough that the hopper is susceptible to clogging. In particular, we measure the average and standard deviation of the distribution of discharged masses as a function of both hole and grain sizes. We do so in air, which is usual, but also with the system entirely submerged under water. This damps the grain dynamics and could be expected to dramatically affect the distribution of the flow events, which are described in prior work as avalanche-like. Though the flow is slower and the events last longer, we find that the average discharge mass is only slightly reduced for submerged grains. Furthermore, we find that the shape of the distribution remains exponential, implying that clogging is still a Poisson process even for immersed grains. Per Thomas and Durian [Phys. Rev. Lett. 114, 178001 (2015)], this allows for an interpretation of the average discharge mass in terms of the fraction of flow microstates that precede, i.e., that effectively cause, a stable clog to form. Since this fraction is barely altered by water, we conclude that the crucial microscopic variables are the grain positions; grain momenta play only a secondary role in destabilizing weak incipient arches. These insights should aid ongoing efforts to understand the susceptibility of granular hoppers to clogging. We report on the nature of flow events for the gravity-driven discharge of glass beads through a hole that is small enough that the hopper is susceptible to clogging. In particular, we measure the average and standard deviation of the distribution of discharged masses as a function of both hole and grain sizes. We do so in air, which is usual, but also with the system entirely submerged under water. This damps the grain dynamics and could be expected to dramatically affect the distribution of the flow events, which are described in prior work as avalanche-like. Though the flow is slower and the events last longer, we find that the average discharge mass is only slightly reduced for submerged grains. Furthermore, we find that the shape of the distribution remains exponential, implying that clogging is still a Poisson process even for immersed grains. Per Thomas and Durian [Phys. Rev. Lett. 114, 178001 (2015)], this allows for an interpretation of the average discharge mass in terms of the fraction of flow microstates that precede, i.e., that effectively cause, a stable clog to form. Since this fraction is barely altered by water, we conclude that the crucial microscopic variables are the grain positions; grain momenta play only a secondary role in destabilizing weak incipient arches. These insights should aid ongoing efforts to understand the susceptibility of granular hoppers to clogging.

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Section: Methodssupporting

confidence: 68%

“…The experimental granular system consists of three sizes of technical quality glass beads (Potters Industries A-series) with material density ρ g = 2.54 ± 0.01 g/cm 3 . The grain diameter distributions are measured using a Retch Technology Camsizer.…”

Section: Methodsmentioning

confidence: 99%

Effect of interstitial fluid on the fraction of flow microstates that precede clogging in granular hoppers

Koivisto

Durian

2017

Phys. Rev. E

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“…Because of its omnipresence in industry and agriculture, one of the most widely studied systems in granular matter is the discharge of grains from a silo [1][2][3][4][5][6][7][8][9][10]. In the pioneering work of Beverloo [2] describing the mass rate Q of grains of size d flowing through an orifice of diameter D under the influence of gravity g, it was found that Q = Cρ b √ g(D − κd) 5/2 , where ρ b is the apparent density of the material and C and κ are constants related to the particle nature and silo geometry.…”

Section: Introductionmentioning

confidence: 99%

“…One of the most relevant aspects of these expressions is the independence of Q on the column height, in contrast to the hydrostatic dependence at the bottom of a water column. Recently, it has been also investigated the granular discharge of submerged hoppers, and a surge in the flow rate was measured at the end of the process [5]. A granular material is usually defined as a conglomerate of macroscopic particles characterized by a loose of energy due to elasticity and friction when particles collide or slide [6].…”

Section: Introductionmentioning

confidence: 99%

Discharge of repulsive grains from a silo: experiments and simulations

2017

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Abstract. In granular matter, sliding friction and collisions among grains are fundamental mechanisms of energy dissipation that determine the particles dynamics. Here we consider an unconventional granular system composed of magnetic repelling grains confined in a two dimensional cell that interact only through their magnetic field. The repulsive interaction prevents contact among grains and therefore produces a different dynamics compared to the dynamics of classical granular systems. In particular, we present experiments and simulations on the discharge of this repulsive granular medium from a silo. The results reveal an inverted density profile and a plug-flow through the aperture that contrast with the dynamics displayed by contacting grains. Moreover, the simulations allow to estimate the friction coefficient generated by the lateral confinement.

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“…The paper by Wilson et al [1] describes experimental results on the discharge of hoppers filled with granular material and immersed in water. The discharge of dry granular matter through hoppers (as well as pipes and silos of various geometries) has been -and is still -much studied, due to the practical importance of these flow geometries but also because of the theoretical difficulties posed by their puzzling behavior.…”

Section: Introductionmentioning

confidence: 99%