Shaking dry powders and grains

Évesque, P.

doi:10.1080/00107519208223973

Cited by 68 publications

(56 citation statements)

References 28 publications

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“…A power law ' 0:1Bo 0:21 g is clearly seen. The extrapolated value for Bo g 1 ( ' 0:1) matches the typical value reported for noncohesive granular materials (Bo g & 1) such as sand [3]. What is the physical origin of this law?…”

supporting

confidence: 66%

“…Walker [1] fitted his data by the logarithmic law 1= ÿ log c = c0 , where is the particle volume fraction, c the applied consolidation stress, and (compression index) and c0 are empirical parameters. This equation applies well in loose samples, where compaction is driven by rearrangement of particles, and has been traditionally used in civil engineering [2,3]. An essential ingredient in most granular systems is cohesion.…”

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confidence: 99%

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Physics of Compaction of Fine Cohesive Particles

2005

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Fluidized fractal clusters of fine particles display critical-like dynamics at the jamming transition, characterized by a power law relating consolidation stress with volume fraction increment [^c / ]. At a critical stress clusters are disrupted and there is a crossover to a logarithmic law ( log^c) resembling the phenomenology of soils. We measure ÿ@ 1= =@ log^c / Bo 0:2 g , where Bo g is the ratio of interparticle attractive force (in the fluidlike regime) to particle weight. This law suggests that compaction is ruled by the internal packing structure of the jammed clusters at nearly zero consolidation. DOI: 10.1103/PhysRevLett.94.075501 PACS numbers: 61.43.Gt, 45.70.Cc, 61.43.Hv, 81.20.Ev Empirical studies on the compaction of soils date back to the beginning of the last century. Walker [1] fitted his data by the logarithmic law 1= ÿ log c = c0 , where is the particle volume fraction, c the applied consolidation stress, and (compression index) and c0 are empirical parameters. This equation applies well in loose samples, where compaction is driven by rearrangement of particles, and has been traditionally used in civil engineering [2,3]. An essential ingredient in most granular systems is cohesion. Tests on cohesive powders show that decreases with the particle volume fraction of the initial state [4,5], indicating that interparticle attractive forces, which favor the formation of porous structures, play a relevant role in the compaction process. Yet the initial state in typical engineering experiments involves consolidation stresses c0 > 10 kPa [5]. Many industry applications demand research on smaller consolidations as these correspond to conditions of powder flow. For example, in the handling of xerographic toners, typical consolidations range from a few pascals to a few hundred pascals. Moreover, experiments at low consolidations have a fundamental interest in order to characterize the transition from the fluidlike to the solidlike state (jamming) [6] since the structural properties of the unconsolidated jammed state ( c ' 0), which is the truly initial state in any compaction process, are determinant on the rearrangement of the further loaded particles. We study the compaction of fine particles with controlled attractive force, initially fluidized and later subjected to loads from just a few pascals up to 10 kPa. Our novel experimental study is aimed to shed light on the role of the initial state, i.e., the unconsolidated jammed state, on compaction. The powders tested are xerographic toners based on polymer (particle density p ' 1 g=cm 3 ). They are produced by an attrition process, thus having an irregular shape, and size classified in a range of particle sizes (d p ) from 19.1 to 7 m by aerodynamic classification, showing a narrow particle size distribution (see Fig. 1). Additionally, the powders are blended with fumed silica nanoparticles (either 8 or 40 nm nominal diameters) to coat uniformly the polymer particle surface in concentrations from 10% to 100% of surface area coverage (SAC).In the fl...

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confidence: 99%

Physics of Compaction of Fine Cohesive Particles

2005

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“…A variety of novel phenomena have been discovered in the past fifteen years [12]: heaping and convection rolls [13,14], standing and traveling waves [15][16][17], oscillons [18], and fluidization [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Velocity statistics in excited granular media

Losert

Cooper

Delour

et al. 1999

Chaos: An Interdisciplinary Journal of Nonlinear Science

267

213

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We present an experimental study of velocity statistics for a partial layer of inelastic colliding beads driven by a vertically oscillating boundary. Over a wide range of parameters (accelerations 3-8 times the gravitational acceleration), the probability distribution P (v) deviates measurably from a Gaussian for the two horizontal velocity components. It can be described by P (v) ∼ exp(−|v/v c | 1.5 ), in agreement with a recent theory. The characteristic velocity v c is proportional to the peak velocity of the boundary. The granular temperature, defined as the mean square particle velocity, varies with particle density and exhibits a maximum at intermediate densities. On the other hand, for free cooling in the absence of excitation, we find an exponential velocity distribution. Finally, we examine the sharing of energy between particles of different mass. The more massive particles are found to have greater kinetic energy. PACS: 83.70.Fn, 05.20.Dd, 83.10.Pp Typeset using REVT E X 1 We determine the statistical properties of particles in a vibrated granular medium experimentally. While many similarities between ordinary gases and excited granular media have been found, a fundamental difference is that collisions between particles in granular matter are inelastic. As a consequence, the velocity distribution deviates measurably from a Gaussian, but can be described by P (v) ∼ exp(−|v/v c | 1.5 ) for a large range of parameters where external excitation is sufficiently frequent, in agreement with a recent theory.

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“…Spontaneous formation of a static heap and convection flow depends on Γ and phase difference Φ [20]. In rectangular container submitted linear horizontal vibration there may be observed two convection rolls; the grains rise at the cell center and dive along the vertical walls [21]. Various types * corresponding author; e-mail: pingwu@sas.ustb.edu.cn of convection cells, convection velocity measurement and mechanisms responsible for different type of motions were discussed [22].…”

Section: Introductionmentioning

confidence: 99%

Convection Rolls and Individual Particles Movements in Horizontally Vibrated Granular Particles System

Rehman

et al. 2016

Acta Phys. Pol. A

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Convection in horizontally vibrated granular systems is significant for scientists and engineers for their importance in the field of mining, geo-physics, and pharmaceutical etc. This research work studied three types of convection rolls, "Homogeneous convection roll", "lower-right diagonal convection roll" and "upper-right diagonal convection roll" which occurred in a square container filled with binary granular particles mixture of sized d = (4.0 ± 0.2) mm and d = (8.0 ± 0.2) mm. Container was vibrated horizontally with low frequencies f and low dimensionless acceleration Γ. Helical movement was observed along the walls perpendicular to direction of motion while straight-line movement along the walls horizontal to direction of motion. Helical and straight-line movements of particles along the walls are the part of convection rolls. A heap appeared due to vibration, which has dominant effect on the convection rolls. Heap position is function of frequency f and dimensionless accelerations Γ.

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Shaking dry powders and grains

Cited by 68 publications

References 28 publications

Physics of Compaction of Fine Cohesive Particles

Physics of Compaction of Fine Cohesive Particles

Velocity statistics in excited granular media

Convection Rolls and Individual Particles Movements in Horizontally Vibrated Granular Particles System

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