Pressure Independence of Granular Flow through an Aperture

Aguirre, M. A.; Grande, Juan; Calvo, A.; Pugnaloni, Luis A.; Géminard, Jean‐Christophe

doi:10.1103/physrevlett.104.238002

Cited by 79 publications

(95 citation statements)

References 22 publications

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“…A similar argument, based in a local pressure reduction, has been used in crowd dynamics to introduce a friction parameter which controls the human clogging [27]. Additionally, let us stress that our results also imply that the pressure reduction does not importantly affect the flow rate, as it has been shown in other experiments [28,29].…”

Section: Prl 107 278001 (2011) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 62%

Silo Clogging Reduction by the Presence of an Obstacle

et al. 2011

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We present experimental results on the effect that inserting an obstacle just above the outlet of a silo has on the clogging process. We find that, if the obstacle position is properly selected, the probability that the granular flow is arrested can be reduced by a factor of 100. This dramatic effect occurs without any remarkable modification of the flow rate or the packing fraction above the outlet, which are discarded as the cause of the change in the clogging probability. Hence, inspired by previous results of pedestrian crowd dynamics, we propose that the physical mechanism behind the clogging reduction is a pressure decrease in the region of arch formation.

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Section: Prl 107 278001 (2011) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 62%

Silo Clogging Reduction by the Presence of an Obstacle

et al. 2011

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“…The contact pressure displays a constant decrease as one approaches the exit. This behavior is practically independent of the aperture size, indicating that the pressure inside the silo does not have a one-to-one relationship with the velocity profile at the exit, as was already suggested in [23]. Meanwhile, the kinetic pressure displays a well-defined maximum near the outlet that defines a transition surface.…”

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confidence: 62%

Disentangling the Free-Fall Arch Paradox in Silo Discharge

et al. 2015

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Several theoretical predictions of the mass flow rate of granular media discharged from a silo are based on the spontaneous development of a free-fall arch region, the existence of which is still controversial. In this Letter, we study experimentally and numerically the particle flow through an orifice placed at the bottom of 2D and 3D silos. The implementation of a coarse-grained technique allows a thorough description of all the kinetic and micromechanical properties of the particle flow in the outlet proximities. Though the free-fall arch does not exist as traditionally understood-a region above which particles have negligible velocity and below which particles fall solely under gravity action-we discover that the kinetic pressure displays a well-defined transition in a position that scales with the outlet size. This universal scaling explains why the free-fall arch picture has served as an approximation to describe the flow rate in the discharge of silos.

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“…Over the years, this equation has been used in diverse situations. Some examples are vibrated silos [9], a system where the material is driven by a conveyor belt [10], mixtures of granular media [11,12], water submerged grains [13], or even the flow of air bubbles through a two-dimensional (2D) slit [14]. However, despite the popularity of the expression of Beverloo et al [8], it involves some features of uncertain physical sense, such as the inclusion of the bulk density ρ B instead of the flowing density or the reduced aperture size D − kd p , which accounts for a hypothetical forbidden area of the orifice through which the beads are not allowed to pass.…”

Section: Introductionmentioning

confidence: 99%

Role of particle size in the kinematic properties of silo flow

2017

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We experimentally analyze the effect that particle size has on the mass flow rate of a quasi two-dimensional silo discharged by gravity. In a previous work, Janda et al. [Phys. Rev. Lett. 108, 248001 (2012)] introduced a new expression for the mass flow rate based on a detailed experimental analysis of the flow for 1-mm diameter beads. Here, we aim to extend these results by using particles of larger sizes and a variable that was not explicitly included in the proposed expression. We show that the velocity and density profiles at the outlet are self-similar and scale with the outlet size with the same functionalities as in the case of 1-mm particles. Nevertheless, some discrepancies are evidenced in the values of the fitting parameters. In particular, we observe that larger particles lead to higher velocities and lower packing fractions at the orifice. Intriguingly, both magnitudes seem to compensate giving rise to very similar flow rates. In order to shed light on the origin of this behavior we have computed fields of a solid fraction, velocity, and a kinetic-stress like variable in the region above the orifice.

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Pressure Independence of Granular Flow through an Aperture

Cited by 79 publications

References 22 publications

Silo Clogging Reduction by the Presence of an Obstacle

Silo Clogging Reduction by the Presence of an Obstacle

Disentangling the Free-Fall Arch Paradox in Silo Discharge

Role of particle size in the kinematic properties of silo flow

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