Bottlenecks in granular flow: When does an obstacle increase the flow rate in an hourglass?

Alonso‐Marroquín, Fernando; Azeezullah, S. I.; Galindo‐Torres, S. A.; Olsen-Kettle, Louise

doi:10.1103/physreve.85.020301

Cited by 64 publications

(62 citation statements)

References 14 publications

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“…In other words, the obstacle basically impedes discharge flow. This result contrasts with a numerical work in which the flow rate shows a peak at a certain L [13]. Although the similar flow rate peak has been reported in experiment [14], its peaks are not very clear.…”

Section: Flow Ratecontrasting

confidence: 55%

Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

Endo

Katsuragi

2017

EPJ Web Conf.

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Abstract. Two-dimensional granular discharge flow driven by gravity under the influence of an obstacle is experimentally investigated. A horizontal exit of width W is opened at the bottom of vertical Hele-Shaw cell filled with stainless-steel particles to start the discharge flow. In this experiment, a circular obstacle is placed in front of the exit. Thus, the distance between the exit and obstacle L is also an important parameter. During the discharge, granular-flow state is acquired by a high-speed camera. The bulk discharge-flow rate is also measured by load cell sensors. The obtained high-speed-image data are analyzed to clarify the particle-level granular-flow dynamics. Using the measured data, we find that the obstacle above the exit affects the granularflow field. Specifically, the existence of obstacle results in large horizontal granular temperature and small packing fraction. This tendency becomes significant when L is smaller than approximately 6D g when W 4D g , where D g is diameter of particles.

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Section: Flow Ratecontrasting

confidence: 55%

Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

Endo

Katsuragi

2017

EPJ Web Conf.

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“…Another scenario in which resemblances among different multiparticle systems has been found is the placement of an obstacle in front of the exit [3,9,16,[22][23][24][25][26][27][28][29][30][31]. Indeed, it has been shown that in such diverse systems as inert grains, ants, mice, and sheep, the presence of the obstacle can improve the flow rate due to the prevention of clogging.…”

Section: Introductionmentioning

confidence: 99%

“…This is, in turn, caused by a reduction in the pressure near the outlet which is related to a density decrease resulting from the appearance of an empty region after the obstacle. Still, a thorough study about the effect of the obstacle position on the evacuation procedures has not been carried out experimentally, although numerical simulations [23] and experiments with inert particles discharged from a silo [25][26][27] are available.…”

Section: Introductionmentioning

confidence: 99%

Effect of obstacle position in the flow of sheep through a narrow door

et al. 2016

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In a recent work [Phys. Rev. E 91, 022808 (2015)] it was reported that placing an obstacle in front of a gate has a beneficial effect in the flow of sheep through it. Here, we extend such results by implementing three different obstacle positions. We have observed that the flow is improved in two cases, while it worsens in the other one; the last instance happens when the obstacle is too close to the door. In this situation, the outcomes suggest that clogging develops between the doorjamb and the obstacle, contrary to the cases when the obstacle is farther, in which case clogging always occurs at the very door. The effectiveness of the obstacle (a strategy put forward to alleviate clogging in emergency exits) is therefore quite sensitive to its location. In addition, the study of the temporal evolution of the flow rate as the test develops makes evident a steady behavior during the entire duration of the entrance. This result is at odds with recent findings in human evacuation tests where the flow rate varies over time, therefore challenging the fairness of straightforward comparisons between pedestrian behavior and animal experimental observations.

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“…Instead, the placement of obstacles is usually aimed to improve the flow and to the reduction of undesirable wall stresses. Indeed, most of the studies about silos and obstacles are performed with such a large outlet size that clogging is practically impossible [14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Flow and clogging in a silo with an obstacle above the orifice

et al. 2012

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In a recent paper [Zuriguel et al., Phys. Rev. Lett. 107, 278001 (2011)] it has been shown that the presence of an obstacle above the outlet can significatively reduce the clogging probability of granular matter pouring from a silo. The amount of this reduction strongly depends on the obstacle position. In this work, we present new measurements to analyze different outlet sizes, extending foregoing results and revealing that the effect of the obstacle is enhanced as the outlet size is increased. In addition, the effect of the obstacle position on the flow rate properties and in the geometrical features of arches is studied. These results reinforce previous evidence of the pressure reduction induced by the obstacle. In addition, it is shown how the mean avalanche size and the average flow rate are not necessarily linked. On the other hand, a close relationship is suggested between the mean avalanche size and the flow rate fluctuations.

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Bottlenecks in granular flow: When does an obstacle increase the flow rate in an hourglass?

Cited by 64 publications

References 14 publications

Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

Effect of obstacle position in the flow of sheep through a narrow door

Flow and clogging in a silo with an obstacle above the orifice

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