Influence of a reduced gravity on the volume fraction of a monolayer of spherical grains

Dorbolo, Stéphane; Scheller, Tom; Ludewig, François; Lumay, Geoffroy; Vandewalle, Nicolas

doi:10.1103/physreve.84.041305

Cited by 6 publications

(5 citation statements)

References 19 publications

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“…Because of slow quasistatic flows, no strong dilation is observed, i.e., no strong dependence of ν on local shear rate. The packing is rather loose for lower p* and tends to a critical value ν = ± 0.642 0.002 c , in agreement with [63]. The data can be fitted well by the functional form…”

Section: Local Volume Fractionsupporting

confidence: 80%

The role of gravity or pressure and contact stiffness in granular rheology

et al. 2015

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The steady-state shear rheology of granular materials is investigated in slow quasistatic and inertial flows. The effect of gravity (thus the local pressure) and the often-neglected contact stiffness are the focus of this study. A series of particle simulations are performed on a weakly frictional granular assembly in a split-bottom geometry considering various magnitudes of gravity and contact stiffnesses. While traditionally the inertial number, i.e., the ratio of stress to strain-rate time scales, is used to describe the flow rheology, we report that a second dimensionless number, the ratio of softness and stress time scales, must also be included to characterize the bulk flow behavior. For slow, quasistatic flows, the density increases while the effective (macroscopic) friction decreases with increase in either particle softness or local pressure. This trend is added to the μ I ( )rheology and can be traced back to the anisotropy in the contact network, displaying a linear correlation between the effective friction coefficient and deviatoric fabric in the steady state. When the external rotation rate is increased towards the inertial regime, for a given gravity field and contact stiffness, the effective friction increases faster than linearly with the deviatoric fabric.

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Section: Local Volume Fractionsupporting

confidence: 80%

The role of gravity or pressure and contact stiffness in granular rheology

et al. 2015

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“…To complete the experimental investigations, we also performed discharge of monolayer silos in low gravity conditions using a similar experimental set-up described in ref. [5]. The results confirm the high gravity outcomes.…”

Section: Introductionsupporting

confidence: 80%

“…The in-plane apparent acceleration depends on the rotation speed. We measured that the density of the packing fraction (at rest) varies from 0.80 to 0.84 while the apparent gravity g ⋆ is increased from 0.05 g to 0.2 g. The packing fraction saturates above g ⋆ = 0.5 g [5]. In the present paper, we investigate the influence of the gravity on a very classical granular material flow: the discharge of a silo.…”

Section: Introductionmentioning

confidence: 94%

Influence of the gravity on the discharge of a silo

et al. 2013

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We performed a series of experiments to investigate the flow of an assembly of non-cohesive spherical grains in both high and low gravity conditions (i.e. above and under the Earth's gravity). In high gravity conditions, we studied the flow of glass beads out of a cylindrical silo and the flow of metallic beads out of a vertical Hele-Shaw rectangular silo. Both silos were loaded in one of the gondolas of the Large Diameter Centrifuge facility (located at ESTEC) in which an apparent gravity up to 20 times the Earth's gravity can be established. To simulate low gravity conditions, we submitted a horizontal monolayer of metallic beads to the centrifuge force of a small rotation device (located at University of Liege). The influences of both gravity and aperture size on the mass flow were analysed in these various conditions. For the three systems (cylindrical silo, the Hele-shaw silo and the monolayer of beads), we demonstrated that (i) the square root scaling of the gravity found by Beverloo is relevant and (ii) the critical aperture size below which the flow is jammed does not significantly increase with the apparent gravity. Moreover, we studied in more details the Hele-Shaw silo in high gravity because this configuration allowed to determine local properties of the flow at the level of the aperture. We measured the velocity profiles and the packing fraction profiles for the various aperture sizes and apparent high gravities. We demonstrate the existence of a slip length for the flow at the level of the aperture. This later fact seems to result from the geometrical configuration of the silo.

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“…Highly stressed grains in static deposits are generally found to form linear structures: the so-called force chains. Notice that, the term "arch" is sometimes used [19,20,21] to refer to these force chains and not to the mutually stabilizing structures defined above. Likewise, the term "dynamic arch" has been used to refer to ephemeral structures that choke the flow of grains [22].…”

Section: Introductionmentioning

confidence: 99%

Arches and contact forces in a granular pile

Carlevaro

Pugnaloni

2012

Eur. Phys. J. E

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Assemblies of granular particles mechanically stable under their own weight contain arches. These are structural units identified as sets of mutually stable grains. It is generally assumed that these arches shield the weight above them and should bear most of the stress in the system. We test such hypothesis by studying the stress born by in-arch and out-of-arch grains. We show that, indeed, particles in arches withstand larger stresses. In particular, the isotropic stress tends to be larger for in-arch grains whereas the anisotropic component is marginally distinguishable between the two types of particles. The contact force distributions demonstrate that an exponential tail (compatible with the maximization of entropy under no extra constraints) is followed only by the out-of-arch contacts. In-arch contacts seem to be compatible with a Gaussian distribution consistent with a recently introduced approach that takes into account constraints imposed by the local force balance on grains.

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Influence of a reduced gravity on the volume fraction of a monolayer of spherical grains

Cited by 6 publications

References 19 publications

The role of gravity or pressure and contact stiffness in granular rheology

The role of gravity or pressure and contact stiffness in granular rheology

Influence of the gravity on the discharge of a silo

Arches and contact forces in a granular pile

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