Article
Physics, Multidisciplinary
Matthew Macaulay, Pierre Rognon
Summary: This study examines the distribution of contact forces in dense granular flows and finds that higher magnitude contact forces exist in faster flows with stiffer grains. A proposed physical mechanism explains this rate-dependent force transmission, establishing a relationship between contact forces and grain velocities. This analysis provides a starting point for unifying a range of continuum models based on either contact forces or grain velocities.
PHYSICAL REVIEW LETTERS
(2021)
Article
Engineering, Chemical
Song Gao, Julio M. Ottino, Paul B. Umbanhowar, Richard M. Lueptow
Summary: In this study, a continuum segregation model and discrete element method simulations were used to explore the segregation of two size-polydisperse particle species with overlapping size distributions. The results suggest that size dispersity has a weak impact on species segregation, and the local species concentration can be accurately modeled as a mixture of two size-monodisperse species, despite the influence of size dispersity on local mean particle size.
CHEMICAL ENGINEERING SCIENCE
(2021)
Article
Engineering, Chemical
T. M. Povall, I Govender, A. T. McBride
Summary: A novel 3D measurement method was proposed to test the compressibility and isotropy of rotating drum flows using the DEM with mu(I) rheology. The study found that compressibility enhances isotropy and statistically better fits were obtained when using an empirically-derived friction law. However, all models failed to capture behavior at very low inertial numbers.
Article
Mechanics
Ishan Srivastava, Leonardo E. Silbert, Gary S. Grest, Jeremy B. Lechman
Summary: This study investigates the flow of dense granular materials under external shear stress and pressure using discrete element method simulations, proposing a rheological model to describe the two types of flow. The simulations show viscometric behavior with non-negligible first and second normal stress differences, highlighting the role of contact fabric tensor and strain rate tensor in determining normal stress differences.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Peter Varun Dsouza, Prabhu R. Nott
Summary: Granular materials exhibit unique features such as dilatancy and large-scale secondary flow driven by a combination of shear and gravity. The height at which the material is filled in a primary flow determines both the shape of the shearing region and the form of the secondary flow, indicating a close coupling between the two phenomena. Unlike fluid instabilities driven by inertia, the secondary flow in granular materials occurs at low shear rates and is an integral part of the kinematic response.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Interdisciplinary Applications
Dorian Faroux, Kimiaki Washino, Takuya Tsuji, Toshitsugu Tanaka
Summary: In this paper, an Eulerian numerical implementation of the non-local granular fluidity model (NGF) is proposed, based on a finite volume method and the volume-of-fluid interface capturing method. The implementation is straightforward and suitable for steady flow problems involving evolving boundaries or two distinct phases.
COMPUTATIONAL PARTICLE MECHANICS
(2022)
Article
Chemistry, Physical
Farnaz Fazelpour, Karen E. Daniels
Summary: In this paper, the influence of boundary shape, particularly roughness, on wall slip in dense granular flows is investigated. Experiments are conducted on a quasi-2D annular shear cell to examine the influence of different boundary properties. It is found that the full flow profile can be accurately captured using a single set of model parameters, with the wall slip velocity set by direct observation. The measurements also reveal a universal relationship between dimensionless fluidity and velocity.
Article
Engineering, Chemical
Wenguang Nan, Mehrdad Pasha, Mojtaba Ghadiri
Summary: Understanding the rheological behavior of fully three-dimensional and non-uniform particle flow is crucial. By analyzing the resistance exhibited by a granular bed as a rotating impeller penetrates into it, the rheological characteristics of the bed can be deduced. The relationship between shear strain rate, inertia number, and bulk friction coefficient differs between spherical and rodlike particles.
Article
Physics, Multidisciplinary
Kuniyasu Saitoh, Takeshi Kawasaki
Summary: We investigated the characteristics of two-dimensional dense granular flows using molecular dynamics simulations. Our results show that the shear-induced diffusion of granular particles exhibits different behaviors at different time scales, and is also influenced by the contact damping model.
FRONTIERS IN PHYSICS
(2022)
Article
Mechanics
T. Barker, C. Zhu, J. Sun
Summary: Vertical chutes and pipes play a crucial role in industrial processes involving powders and grains. Through simulations and idealizations, the study reveals linear scaling laws and a novel rheology model for vertical flow, providing insights into the behavior of different flow regimes. The research highlights a linear relation between chute width and shear zone size, contrasting with previous findings and suggesting minimal finite-size effects for the inertial flows studied.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Multidisciplinary Sciences
Ashta Navdeep Karuriya, Francois Barthelat
Summary: This article introduces a method for producing fully dense 3D architectural materials by assembling building particles into crystalline structures using mechanical vibrations. Experimental results show that these granular crystals are 25 times stronger than randomly packed spheres and can be recycled. The study also reveals interesting mechanisms such as nonlinear deformation, crystal plasticity, and pressure-dependent plasticity.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Engineering, Chemical
Guangyang Hong, Jian Bai, Jian Li, Qijun Zheng, Aibing Yu
Summary: Dense driven granular materials have complex rheological phenomena, and the unjamming/yielding transition induced by intruder deformation is poorly understood. In this study, we investigate the relaxation dynamics of a granular medium driven by oscillatory intruder deformation and observe an abrupt unjamming/yielding transition in the frequency domain. This transition is characterized by the emergence of vortices, shear bands, and a transformation in spatial correlations.
Article
Chemistry, Physical
Farnaz Fazelpour, Zhu Tang, Karen E. Daniels
Summary: In this paper, the authors conducted experiments to investigate the influence of particle properties on the model parameters used in the nonlocal rheology. They found that different particle shapes and materials have significant effects on the nonlocal parameter, indicating the dominance of geometric friction over material friction.
Article
Geochemistry & Geophysics
N. Casas, G. Mollon, A. Daouadji
Summary: Fault zones are composed of granular gouge, which contributes to friction stability. Different infill materials can be observed in mature fault zones, changing the rheological and frictional behaviors of the gouge. The study aims to understand the influence of grain-scale characteristics on slip mechanisms and gouge rheology by using the discrete element method. The findings suggest that gouge materials with high interparticle friction or high shear modulus may lead to faster earthquake ruptures.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Engineering, Chemical
Jianbo Fei, Yuxin Jie, Hao Xiong, Chengyu Hong
Summary: This study establishes a continuum model with dynamic earth pressure coefficient to describe granular slump process and quantify normal stresses. The simulation results show that the proposed dynamic model captures important features of granular slump process and can reproduce the inner static sided axisymmetric region observed in tests.