Heterogeneities in granular materials

Mehta, Anita; Barker, G. C.; Luck, J. M.

doi:10.1063/1.3141940

Cited by 32 publications

(34 citation statements)

References 19 publications

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“…Within this picture, shear thickening and jamming are viewed as a type of stress induced glass transition, for which the applied stress inhibits particle motion, even in the absence of hydrodynamics. A number of works have suggested a relationship between shear thickening and jamming [3,4,108,126] although details of the connection between hydrodynamic cluster formation and jamming transitions of the kind more familiar from studies of granular media [127] remains unclear.…”

Section: Shear Thickeningmentioning

confidence: 99%

Nonlinear rheology of colloidal dispersions

Brader¹

2010

J. Phys.: Condens. Matter

128

156

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Colloidal dispersions are commonly encountered in everyday life and represent an important class of complex fluid. Of particular significance for many commercial products and industrial processes is the ability to control and manipulate the macroscopic flow response of a dispersion by tuning the microscopic interactions between the constituents. An important step towards attaining this goal is the development of robust theoretical methods for predicting from first-principles the rheology and nonequilibrium microstructure of well defined model systems subject to external flow. In this review we give an overview of some promising theoretical approaches and the phenomena they seek to describe, focusing, for simplicity, on systems for which the colloidal particles interact via strongly repulsive, spherically symmetric interactions. In presenting the various theories, we will consider first low volume fraction systems, for which a number of exact results may be derived, before moving on to consider the intermediate and high volume fraction states which present both the most interesting physics and the most demanding technical challenges. In the high volume fraction regime particular emphasis will be given to the rheology of dynamically arrested states.

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Section: Shear Thickeningmentioning

confidence: 99%

Nonlinear rheology of colloidal dispersions

Brader¹

2010

J. Phys.: Condens. Matter

128

156

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“…However, in concentrated particle suspensions, we can see characteristic rheological properties such as shear-thickening (18) and rich flow behavior as compared to the flow of dilute suspensions (16), (19), (20) . Furthermore, numerical simulations for concentrated suspensions are necessary in practical point of view because they are often applied in manufacturing various products.…”

Section: Suspensions Of Disclike Particlesmentioning

confidence: 99%

Numerical Simulation of Extrusion Flows of Polymer Melts and Disclike Particle Suspensions Based on Stochastic Calculation of Their Mesoscale Structures

Shimizu

Yamamoto

2010

JFST

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Flows of complex fluids in a single-screw extruder were numerically simulated using a coupling method of continuum-mechanics-based computations for macroscopic flows and stochastic simulations for fluid mesoscale structures and the advantage of micro-macro simulations for complex fluids was investigated. In the present study, flows of polymer melts and dilute suspensions of disclike particles were considered and a simple model for the extrusion flow in which the flow is approximated by a shallow channel flow, was adopted. In the simulation for polymer melts, the Curtiss-Bird model was applied to represent the dynamics of polymer networks. The orientation behavior of polymers was analyzed and its dependence on the Weissenberg number was investigated. In addition, a low-cost method for plotting the distribution of orientation angle of polymers was proposed. In this method, additional stochastic simulation was performed at a sampling point in the flow field. The dependence of orientation angle on the gap wise position in an extruder was captured in more detail by this method. In the simulation of suspensions of disclike particles, a disclike particle was modeled by an oblate spheroid, and the motion of particles was computed using the stochastic differential equation for orientation vectors of oblate spheroids. The orientation behavior of particles was analyzed to find that the present approach is effective also for the suspension flows.

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“…The load-bearing properties of concentrated particulates and their stability under gravity or other external forces are key issues for soils, powders, ceramics, colloids, porous media, packed bed reactors and many other applications. Load-bearing properties have been linked to structural ''bridges'', a concept developed in the analysis of computer simulations of granulars [1][2][3][4][5][6][7][8]. Particles belonging to a given bridge mutually stabilize each other against an applied force, such as gravity.…”

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confidence: 99%

“…Particles belonging to a given bridge mutually stabilize each other against an applied force, such as gravity. Bridges can have various architectures, ranging from linear [5][6][7] to more complex, branched structures [6][7][8]. While the bridge size distributions, PðmÞ, putatively link the particle configuration and the load-bearing properties of a packing, aspects of the nature of this relationship remain obscure.…”

mentioning

confidence: 99%

“…We studied hard-sphere colloidal suspensions across a range of low to moderate Pe (Pe % 10 À3 and % 4), which was varied via the degree of density matching. Confocal microscopy was used to record particle coordinates [22,23], from which, based on geometrical methods from granular simulations [4][5][6][7][8], we identified bridges [24] and determined bridge size distributions. We compared these with results from granular simulations, whose intention was to reveal how structures able to bear a load are related to an applied external load.…”

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confidence: 99%

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Does Gravity Cause Load-Bearing Bridges in Colloidal and Granular Systems?

et al. 2011

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We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings.

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Heterogeneities in granular materials

Abstract: Different parts of a sandpile can exhibit very different dynamical behaviors ranging from jammed to fluid. To understand them, one needs to look at the networks of contacts between individual grains.

Cited by 32 publications

References 19 publications

Nonlinear rheology of colloidal dispersions

Nonlinear rheology of colloidal dispersions

Numerical Simulation of Extrusion Flows of Polymer Melts and Disclike Particle Suspensions Based on Stochastic Calculation of Their Mesoscale Structures

Does Gravity Cause Load-Bearing Bridges in Colloidal and Granular Systems?

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