The effect of grain shape and material on the nonlocal rheology of dense granular flows

Fazelpour, Farnaz; Tang, Zhu; Daniels, Karen E.

doi:10.1039/d1sm01237a

Cited by 19 publications

(26 citation statements)

References 37 publications

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“…where the nonlocal parameter A is an experimentally-determined constant for a particular set of particles 25 and indicates the strength of their nonlocal effects. ξ is symmetric and most sensitive near the yield criterion µ s .…”

Section: The Cooperative Modelmentioning

confidence: 99%

“…The cooperative model has been validated in both 2D and 3D simulations 20,21,27 and in 2D experiments (annular Couette) 24,25 . While b need only be a quantity near unity, the local and nonlocal parameters µ s , A are constants and a function of both material properties and particle shape 25 ; they need to be determined separately, for each new set of particles. Once these parameters are known, the cooperative model can model granular flows by solving Eq.…”

Section: The Cooperative Modelmentioning

confidence: 99%

“…The curvature of the four solid walls is denoted as O = outies and I = innies. The 52 leafsprings, each of which compresses approximately linearly under stress, are the same walls used in Tang et al 24 , Fazelpour et al 25 . In all the datasets, the inner wall has an S.I.…”

Section: Apparatusmentioning

confidence: 99%

“…The particles used in all six datasets are photoelastic disks made of Vishay PhotoStress material PSM-4 (bulk modulus E = 4 MPa and density ρ = 1.06 g/cm 3 ). These are the same particles used in Fazelpour et al 25 , Owens and Daniels 28 , 29 . The mixture has an equal population of bidisperse circles with diameter d S = 0.9 cm and d L = 1.1 cm and thickness 6.35 mm.…”

Section: Apparatusmentioning

confidence: 99%

“…We have previously observed that this model can successfully capture granular flows in a 2D annular rheometer across various packing fractions and shearing rates, 24 as well as for a variety of particle stiffnesses and shapes. 25 In both cases, a single set of nonlocal parameters can be assigned to a particular set of particles. However, in order for a nonlocal model to be a successful predictive tool, it will be necessary to make flow measurements for a set of particles in one geometry, and then use them to provide predictions for flows in other geometries.…”

Section: Introductionmentioning

confidence: 99%

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Controlling rheology via boundary conditions in dense granular flows

Fazelpour¹,

Daniels²

2022

Preprint

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Boundary shape, particularly roughness, strongly controls the amount of wall slip in dense granular flows. In this paper, we aim to quantify and understand which aspects of a dense granular flow are controlled by the boundary condition, and to incorporate these observations into a cooperative nonlocal model characterizing slow granular flows. To examine the influence of boundary properties, we perform experiments on a quasi-2D annular shear cell with a rotating inner wall and a fixed outer wall; the later is selected from among 6 walls with various roughness, local concavity, and compliance. We find that we can successfully capture the full flow profile using a single set of empirically determined model parameters, with only the wall slip velocity set by direct observation. Through the use of photoelastic particles, we observe how the internal stresses fluctuate more for rougher boundaries, corresponding to lower wall slip, and connect this observation to the propagation of nonlocal effects originating at the wall.

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Section: The Cooperative Modelmentioning

confidence: 99%

Section: The Cooperative Modelmentioning

confidence: 99%

Section: Apparatusmentioning

confidence: 99%

Section: Apparatusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Controlling rheology via boundary conditions in dense granular flows

Fazelpour¹,

Daniels²

2022

Preprint

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Understanding the interplay between particle shape, grading and sample density on the behaviour of granular assemblies: A DEM approach

Adesina,

O’Sullivan,

Wang

2024

Granular Matter

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This study investigates the interplay between particle shape, grading and initial sample density, three of the most important factors influencing the mechanical behaviour of sheared granular assemblies. Using the discrete element method (DEM), two-dimensional assemblies of varying initial sample density, particle aspect ratio, $$AR$$ AR , and coefficients of uniformity, $${C}_{u}$$ C u , were prepared and subjected to drained biaxial shearing until the critical state was reached. We assessed the interplay between each of these parameters by evaluating whether the effect of any given parameter on a mechanical quantity is influenced by any other parameter. Our analyses show that the effect of some of these key parameters on mechanical response, can indeed be influenced by other key parameters. The effect of the particle $$AR$$ AR on the peak shear strength for the initially dense assemblies differs when compared with the medium-dense assemblies. The mechanical coordination number of the assemblies at the initial state correlates with the peak strength thereby explaining the interplay between particle $$AR$$ AR and initial sample density on the peak shear strength. The linear relationship established between strength and dilatancy for a combination of all assemblies studied suggests that the strength-dilatancy relationship is a unique characteristic of granular assemblies. The dilatancy of the assemblies correlates strongly with the amount of contacts lost during shearing. The interplays found between particle shape, grading and initial sample density in this study show that to develop robust constitutive models for the prediction of granular material behaviour, the effects of multiple factors must be considered. Graphic abstract

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DEM study on the effect of particle shape on the shear behaviour of granular materials

2023

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This study investigates the effects of particle convexity, sphericity and aspect ratio (AR) on the behaviour of sheared granular materials using two-dimensional discrete element method simulations. Isotropic, dense and loose assemblies with different particle shapes were prepared and subjected to drained shearing via biaxial compression until the critical state was reached. Macroscopic characteristics such as strength and dilatancy are presented. The factors underlying the macroscopic behaviour are then investigated by considering the coordination number, fabric anisotropy, particle moment, friction mobilisation at contacts and particle rotation. For the range of shapes considered here, the data indicate that the shear strength decreases as particle convexity and sphericity increases while the shear strength increases with increasing AR. The shear strength and convexity are weakly correlated, however a stronger correlation is observed between AR and strength. The volumetric strain at large strains tends to increase with increasing AR. There is a stronger correlation between the critical state strength and both the critical state coordination number and the critical state mechanical void ratio than there is between the critical state void ratio and the critical state strength. The contact fabric anisotropy, the magnitude of the moment transmitted by particles and the friction mobilised at the contacts are important factors underlying strength. The critical state strength increases as both the mean particle moment and the mean mobilised friction increased. Analysis of particle rotation provides insights into the response of the granular materials to shearing.

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The effect of grain shape and material on the nonlocal rheology of dense granular flows

Abstract: Nonlocal rheologies allow for the modeling of granular flows from the creeping to intermediate flow regimes, using a small number of parameters. In this paper, we report on experiments testing...

Cited by 19 publications

References 37 publications

Controlling rheology via boundary conditions in dense granular flows

Controlling rheology via boundary conditions in dense granular flows

Understanding the interplay between particle shape, grading and sample density on the behaviour of granular assemblies: A DEM approach

DEM study on the effect of particle shape on the shear behaviour of granular materials

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