Transition due to base roughness in a dense granular flow down an inclined plane

Kumaran, V.; Maheshwari, Siddharth

doi:10.1063/1.4710543

Cited by 29 publications

(27 citation statements)

References 51 publications

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“…Such a technique, which is able to reproduce successfully the experimental results in many configurations (e.g., gravity-driven flows [1,2,21,22], sheared systems [3,23], granular materials close to jamming [24], silos [25], and rotating drums [26,27]), requires giving an explicit expression for the inter-particle forces. The discrete element method is classical and well known and can found in the aforementioned references.…”

Section: Dem Simulations a Methods And Parametersmentioning

confidence: 99%

Average balance equations, scale dependence, and energy cascade for granular materials

Artoni¹,

Richard²

2015

Phys. Rev. E

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A new averaging method linking discrete to continuum variables of granular materials is developed and used to derive average balance equations. Its novelty lies in the choice of the decomposition between mean values and fluctuations of properties which takes into account the effect of gradients. Thanks to a local homogeneity hypothesis, whose validity is discussed, simplified balance equations are obtained. This original approach solves the problem of dependence of some variables on the size of the averaging domain obtained in previous approaches which can lead to huge relative errors (several hundred percentages). It also clearly separates affine and nonaffine fields in the balance equations. The resulting energy cascade picture is discussed, with a particular focus on unidirectional steady and fully developed flows for which it appears that the contact terms are dissipated locally unlike the kinetic terms which contribute to a nonlocal balance. Application of the method is demonstrated in the determination of the macroscopic properties such as volume fraction, velocity, stress, and energy of a simple shear flow, where the discrete results are generated by means of discrete particle simulation.

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Section: Dem Simulations a Methods And Parametersmentioning

confidence: 99%

Average balance equations, scale dependence, and energy cascade for granular materials

Artoni¹,

Richard²

2015

Phys. Rev. E

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“…For instance, the minimum thickness necessary to sustain a steady flow down incline is a function of base roughness [1]; the fingering instability developed at the front of granular avalanches is due to the change of basal resistance upon segregation [2][3][4]; an inadequate base roughness may be responsible for the unsteady flow regime and crystallisation in chute flows [5][6][7]; in smallscale experimental debris flows, base roughness is the key to produce a realistic deposition with levee formation [8].…”

Section: Introductionmentioning

confidence: 99%

Effect of geometric base roughness on size segregation

et al. 2017

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Abstract. The geometric roughness at boundaries has a profound impact on the dynamics of granular flows. For a bumpy base made of fixed particles, two major factors have been separately studied in the literature, namely, the size and spatial distribution of base particles. A recent work has proposed a roughness indicator R a , which combines both factors for any arbitrary bumpy base comprising equally-sized spheres. It is shown in mono-disperse flows that as R a increases, a transition occurs from slip (R a < 0.51) to non-slip (R a > 0.62) conditions. This work focuses on such a phase transition in bi-disperse flows, in which R a can be a function of time. As size segregation takes place, large particles migrate away from the bottom, leading to a variation of size ratio between flow-and base-particles. As a result, base roughness R a evolves with the progress of segregation. Consistent with the slip/non-slip transition in mono-disperse flows, basal sliding arises at low values of R a and the development of segregation might be affected; when R a increases to a certain level (R a > 0.62), non-slip condition is respected. This work extends the validity of R a to bi-disperse flows, which can be used to understand the geometric boundary effect during segregation.

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“…The most detailed studies of order-disorder transitions in granular shear flow are computational, using the discrete element method (DEM) to simulate the flow of monodisperse particles (diameter d) on a rough inclined plane with periodic boundary conditions (no sidewalls) [19][20][21]. Kumaran and Maheshwari [20] carried out a study of the transition using a base comprising particles of diameter, d b , arranged on a square lattice.…”

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confidence: 99%

“…Kumaran and Maheshwari [20] carried out a study of the transition using a base comprising particles of diameter, d b , arranged on a square lattice. When the base roughness parameter (d b /d) was less than 0.6, the system underwent a transition to an ordered state, comprising hexagonally close packed particle layers sliding on each other.…”

mentioning

confidence: 99%

“…Shear stresses are consequently lower compared to the disordered state. Order-disorder transitions thus affect system behavior significantly, however, they have not been explicitly incorporated in the analysis of granular rheology.The most detailed studies of order-disorder transitions in granular shear flow are computational, using the discrete element method (DEM) to simulate the flow of monodisperse particles (diameter d) on a rough inclined plane with periodic boundary conditions (no sidewalls) [19][20][21]. Kumaran and Maheshwari [20] carried out a study of the transition using a base comprising particles of diameter, d b , arranged on a square lattice.…”

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Sidewall-friction-driven ordering transition in granular channel flows: Implications for granular rheology

Mandal

Khakhar

2017

Phys. Rev. E

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We report a transition from a disordered state to an ordered state in the flow of nearly monodisperse granular matter flowing in an inclined channel with a bumpy base, in discrete element method simulations. For low particle-sidewall friction coefficients, the particles are disordered and the Bagnold velocity profile is obtained. However, for high sidewall friction, an ordered state is obtained, characterized by a layering of the particles and hexagonal packing of the particles in each layer. The extent of ordering, quantified by the local bond-orientational order parameter, varies in the crosssection of the channel, with the highest ordering near the side walls. The flow transition significantly affects the local rheology -the effective friction coefficient is lower, and the packing fraction is higher, in the ordered state compared to the disordered state. A simple model, incorporating the extent of local ordering, is shown to describe the rheology of the system.Understanding the flow of granular materials is important in the context of natural phenomena and industrial processes [1][2][3][4][5]. Considerable progress has been made in the development of theories for the rheology of granular flows, with the objective of developing continuum models for the analysis and design of large systems [6][7][8][9][10]. Granular materials exhibit many complex phenomena [11,12]. The ordering of monodisperse granular materials, when subjected to vibration or shear flow, is one example [13][14][15][16][17][18]. The transition from a disordered state to an ordered state is marked by a significant increase in the solid fraction manifested as a compaction of the material [13,17]. In sheared systems, which are the focus of the present study, ordered states show a layering of particles with adjacent particle layers sliding past each other without much interchange of particles between the layers [15,16,19]. Shear stresses are consequently lower compared to the disordered state. Order-disorder transitions thus affect system behavior significantly, however, they have not been explicitly incorporated in the analysis of granular rheology.The most detailed studies of order-disorder transitions in granular shear flow are computational, using the discrete element method (DEM) to simulate the flow of monodisperse particles (diameter d) on a rough inclined plane with periodic boundary conditions (no sidewalls) [19][20][21]. Kumaran and Maheshwari [20] carried out a study of the transition using a base comprising particles of diameter, d b , arranged on a square lattice. When the base roughness parameter (d b /d) was less than 0.6, the system underwent a transition to an ordered state, comprising hexagonally close packed particle layers sliding on each other. The shear stress (τ xy ) in the ordered state followed the Bagnold scaling (τ xy ∝γ 2 , whereγ is the shear rate) but with smaller values of the Bagnold coefficients compared to the disordered state. The transition was very sharp, occurring over a 1% change in the roughness parameter. A...

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Transition due to base roughness in a dense granular flow down an inclined plane

Cited by 29 publications

References 51 publications

Average balance equations, scale dependence, and energy cascade for granular materials

Average balance equations, scale dependence, and energy cascade for granular materials

Effect of geometric base roughness on size segregation

Sidewall-friction-driven ordering transition in granular channel flows: Implications for granular rheology

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