Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y43: Flow and Packing of Dense Granular MaterialsInvited Live Streamed
|
Hide Abstracts |
Sponsoring Units: GSNP DSOFT Chair: Gary Grest, Sandia National Laboratories Room: McCormick Place W-375B |
Friday, March 18, 2022 8:00AM - 8:36AM |
Y43.00001: Rheology of Cohesive Granular Media Invited Speaker: Olivier Pouliquen Characterization and prediction of the `flowability' of powders are of paramount importance in many industries. However, our understanding of the flow of powders is sparse compared to the flow of coarse granular media. The main difficulty comes from the presence of adhesive forces between the grains, preventing smooth and continuous flows. In this talk we will first present results from discrete simulations, showing that contrary to what is commonly perceived, the cohesive nature of the flow is not entirely controlled by the inter-particle adhesion, but that stiffness and inelasticity of the grains also play a significant role. We also analyzed the development of shear banding and relates it to the existence of a shear weakening branch in the rheology of cohesive grains. In a second part, I will present an experimental work in which we have developed a method for preparing a granular material with a controlled adhesion between particles. The granular material is made of spherical glass beads coated with a polyborosiloxane polymer. This material is proved to be stable in time and non-sensitive to temperature and humidity, opening many perspectives to experimentally study the flow of cohesive grains in a controlled manner. |
Friday, March 18, 2022 8:36AM - 9:12AM |
Y43.00002: Coupling rheology and segregation in granular flows Invited Speaker: J. M. N. T Gray During the last fifteen years there has been a paradigm shift in the continuum modelling of granular materials; most notably with the development of rheological models, such as the μ(I)-rheology, but also with significant advances in theories for particle segregation. This paper details theoretical and numerical frameworks (based on OpenFOAM®) which unify these currently disconnected endeavours. Coupling the segregation with the flow, and vice versa, is not only vital for a complete theory of granular materials, but is also beneficial for developing numerical methods to handle evolving free surfaces. This general approach is based on the partially regularized incompressible μ(I)-rheology, which is coupled to the gravity-driven segregation theory of Gray & Ancey (J. Fluid Mech., vol. 678, 2011, pp. 353–588). These advection–diffusion–segregation equations describe the evolving concentrations of the constituents, which then couple back to the variable viscosity in the incompressible Navier–Stokes equations. A novel feature of this approach is that any number of differently sized phases may be included, which may have disparate frictional properties. Further inclusion of an excess air phase, which segregates away from the granular material, then allows the complex evolution of the free surface to be captured simultaneously. Three primary coupling mechanisms are identified: (i) advection of the particle concentrations by the bulk velocity, (ii) feedback of the particle-size and/or frictional properties on the bulk flow field and (iii) influence of the shear rate, pressure, gravity, particle size and particle-size ratio on the locally evolving segregation and diffusion rates. The numerical method is extensively tested in one-way coupled computations, before the fully coupled model is compared with the discrete element method simulations and used to compute the petal-like segregation pattern that spontaneously develops in a square rotating drum. |
Friday, March 18, 2022 9:12AM - 9:48AM |
Y43.00003: Flow and Packing of Dense Granular Materials Invited Speaker: Leo Silbert Packings of frictional, bidisperse spheres can attain packing fractions larger than the values attributed to the corresponding random loose and close packing limits: nominally identified over the range, 0.55 – 0.64 in packing fraction. It is also known that excitation of a given packing, such as through tapping, can lead to further compaction. Here, we explore just how high can the packing fraction for frictional, bidisperse packings go, using large-scale, pressure-controlled discrete element simulations. Our binary sphere packings span a wide range in particle size ratio, up to 40:1, over several orders of magnitude in particle friction coefficient. Starting from the densest stable state, these packings are subject to small amplitude and low frequency oscillations, then allowed to slowly evolve over time (of the order of 107 simulation timesteps). We compare and contrast the structural evolution of the different packings in an effort to identify common behavior during the vibration process. |
Friday, March 18, 2022 9:48AM - 10:24AM |
Y43.00004: Memory in three-dimensional cyclically driven granular material Invited Speaker: Wolfgang Losert Dense granular packings are often subjected to cyclic forcing, and it is critical to understand whether such forcing will lead to irreversible rearrangements of particles, which can result in creep, yielding, or segregation. It is known that the response to forcing depends on the prior history of the packing, i.e. the system has a memory of prior rearrangements. The role of rotations is of particular interest, since most energy dissipation in driven dense granular packings occurs through frictional sliding during particle rotations. We measure a three-dimensional granular system's reversibility and memory under cyclic compression through a combination of experiments directly matched with simulations. Experimentally, we image the grains using a refractive-index-matched fluid, then analyze the images using the artificial intelligence of variational autoencoders. These techniques allow us to track all the grains' translations and three-dimensional rotations with accuracy sufficient to infer contact-point sliding and rolling. We match these experimental observations to simulations, which allow us to dissect the role of translations and rotations in granular memory. Our observations reveal unique roles played by three-dimensional rotations in granular flow, memory, and energy dissipation. |
Friday, March 18, 2022 10:24AM - 11:00AM |
Y43.00005: Nucleation and propagation of fracture at a fricitonal interface Invited Speaker: Matthieu Wyart Slip at a frictional interface occurs via intermittent events. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700