Internal Granular Dynamics, Shear-Induced Crystallization, and Compaction Steps

Tsai, Jih-Chiang; Voth, Greg; Gollub, Jerry P.

doi:10.1103/physrevlett.91.064301

Cited by 123 publications

(119 citation statements)

References 14 publications

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“…The most significant density variations were observed for the case P 10V 50 corresponding to a light fast moving upper plate. The horizontal velocity decays roughly exponentially off the plate in agreement with experimental evidence [2,7]. The vertical profiles of the order parameter demonstrate a well-defined transition from fluid state near the upper plate to solid state below.…”

Section: Surface-driven Shear Granular Flow Under Gravitysupporting

confidence: 69%

“…In the last few year there have been many experimental [1,2,3,4,5,6,7] and theoretical [8,9,10,11,12,13,14] studies that explored a broad range of granular flow conditions from rapid dilute flows to slow dense flows, as well as the details of the shear-driven fluidization transition. While dilute granular flows can be well described by the kinetic theory of dissipative granular gases [15], dense granular flows still present significant difficulty in formulation of a continuous theory.…”

Section: Introductionmentioning

confidence: 99%

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Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

2003

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The continuum theory of partially fluidized shear granular flows is tested and calibrated using two dimensional soft particle molecular dynamics simulations. The theory is based on the relaxational dynamics of the order parameter that describes the transition between static and flowing regimes of granular material. We define the order parameter as a fraction of static contacts among all contacts between particles. We also propose and verify by direct simulations the constitutive relation based on the splitting of the shear stress tensor into a"fluid part" proportional to the strain rate tensor, and a remaining "solid part". The ratio of these two parts is a function of the order parameter. The rheology of the fluid component agrees well with the kinetic theory of granular fluids even in the dense regime. Based on the hysteretic bifurcation diagram for a thin shear granular layer obtained in simulations, we construct the "free energy" for the order parameter. The theory calibrated using numerical experiments with the thin granular layer is applied to the surface-driven stationary two dimensional granular flows in a thick granular layer under gravity.

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Section: Surface-driven Shear Granular Flow Under Gravitysupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

2003

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“…Granular materials persist at the forefront of contemporary research due to the extreme richness in their dynamics, either under shear [1], flowing out of a hopper [2], or driven by gravity [3]. Because thermodynamic temperature plays little role in determining these features, granular materials are widely recognized as a macroscopic analogue of athermal systems far from equilibrium [4].…”

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confidence: 99%

Temporally Heterogeneous Dynamics in Granular Flows

Silbert

2005

Phys. Rev. Lett.

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Granular simulations are used to probe the particle scale dynamics at short, intermediate, and long time scales for gravity driven, dense granular flows down an inclined plane. On approach to the angle of repose, where motion ceases, the dynamics become intermittent over intermediate times, with strong temporal correlations between particle motionstemporally heterogeneous dynamics. This intermittency is characterised through large scale structural events whereby the contact network periodically spans the system. A characteristic time scale associated with these processes increases as the stopped state is approached. These features are discussed in the context of the dynamics of supercooled liquids near the glass transition.

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“…Using a fluorescence technique [4,7,8], we obtain the packing of glass spheres before and after application of cyclic shear, and compare with random packing of frictionless spheres. We find that the overall shape of g(r) for volume fraction φ ∼ 0.6 is captured by the Percus-Yevick equation [9] which assumes random packing of spheres without angular correlations.…”

mentioning

confidence: 99%

Spatial distribution functions of random packed granular spheres obtained by direct particle imaging

Panaitescu

Kudrolli

2010

Phys. Rev. E

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We measure the two-point density correlations and Voronoi cell distributions of cyclically sheared granular spheres obtained with a fluorescence technique and compare them with random packing of frictionless spheres. We find that the radial distribution function g(r) is captured by the PercusYevick equation for initial volume fraction φ = 0.59. However, small but systematic deviations are observed because of the splitting of the second peak as φ is increased towards random close packing. The distribution of the Voronoi free volumes deviates from postulated Γ distributions, and the orientational order metric Q6 shows disorder compared to numerical results reported for frictionless spheres. Overall, these measures show significant similarity of random packing of granular and frictionless spheres, but some systematic differences as well. The packing of spheres is one of the enduring problems in physics, and a basis to understand the structure and strength of granular matter. Assuming dominance of steric interactions, dense packing of steel spheres was first used to understand structure of simple liquids with the radial distribution function g(r) and the orientation order metric Q 6 [1]. However, experimental measurements at boundaries [2] and computer simulations in the bulk [3] have since shown that inter-particle friction can affect granular packing. Friction between particles changes the fundamental stability condition at contact from the frictionless case, causing a packing to be protocol dependent and the system to be out-of-equilibrium.The difficulty of accurately measuring significant number of particle positions in the bulk away from the influence of boundaries has also stymied progress. Recent experimental studies [4,5] have examined packing of granular spheres and find that the associated free volume distributions are described by a Γ distribution with two fitting parameters which were then given a thermodynamic interpretation [5]. These results are puzzling in light of earlier analytical work in one-dimension and simulations in two and three dimensions that show a Γ distribution with 3 fitting parameters is needed to describe a broad range of volume fraction for elastic particles [6].Here, we discuss new experiments with spherical granular particles which enable us to directly determine statistical measures to understand the effect of friction, test the effect of shear, and perform a rigorous comparison with frictionless hard sphere packing. Using a fluorescence technique [4,7,8], we obtain the packing of glass spheres before and after application of cyclic shear, and compare with random packing of frictionless spheres. We find that the overall shape of g(r) for volume fraction φ ∼ 0.6 is captured by the Percus-Yevick equation [9] which assumes random packing of spheres without angular correlations. But, systematic deviations are observed because of the splitting of the second peak as φ is increased toward random close packing, Q 6 shows partial hexagonal order, and the distribution of the Voronoi free T...

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Internal Granular Dynamics, Shear-Induced Crystallization, and Compaction Steps

Cited by 123 publications

References 14 publications

Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

Partially fluidized shear granular flows: Continuum theory and molecular dynamics simulations

Temporally Heterogeneous Dynamics in Granular Flows

Spatial distribution functions of random packed granular spheres obtained by direct particle imaging

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