Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session A30: Granular Flows: Jamming and Drag |
Hide Abstracts |
Chair: Dong Wang, Duke University Room: F151 |
Sunday, November 20, 2016 8:00AM - 8:13AM |
A30.00001: Origins of Shear Jamming for Frictional Grains Dong Wang, Hu Zheng, Jie Ren, Joshua Dijksman, Jonathan Bares, Robert Behringer Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. [Preview Abstract] |
Sunday, November 20, 2016 8:13AM - 8:26AM |
A30.00002: Shear jamming in highly strained granular system without shear banding Yiqiu Zhao, Jonathan Barés, Hu Zheng, Robert Behringer Bi et al. (Nature 2011) have shown that, if sheared, a granular material can jam even if its packing fraction ($\phi )$ is lower than the critical isotropic jamming point $\phi $J. They have introduced a new critical packing fraction value $\phi $S such that for $\phi $S\textless $\phi $\textless $\phi $J the system jams if sheared. Nevertheless, the value of $\phi $S as a function of the shear profile or the strain necessary to observe jamming remain poorly understood because of the experimental complexity to access high strain without shear band. We present a novel 2D periodic shear apparatus made of 21 independent, aligned and mirrored glass rings. Each ring can be moved independently which permits us to impose any desired shear profile. The circular geometry allows access to any strain value. The forces between grains are measured using reflective photoelasticity. By performing different shear profiles for different packing fractions we explored the details of jamming diagram including the location of the yield surface. [Preview Abstract] |
Sunday, November 20, 2016 8:26AM - 8:39AM |
A30.00003: Jamming transition of angular shaped particles under compression Cacey Stevens Bester, Yiqiu Zhao, Yuanyuan Xu, Meredith Cox, Robert Behringer A fundamental challenge of understanding the global behavior of granular assemblies is to determine the effect of local particle properties, such as particle shape. Here we investigate how particle shape influences the jamming transition of granular packings by comparing the response of systems of angular shaped particles to that of disks under isotropic compression. These experiments are performed using two-dimensional arrangements of photoelastic particles, allowing us to visualize the change in force propagation during the jamming transition. We find qualitative and quantitative differences in the macroscopic responses of the systems with changing particle shape. We compare the packing fraction and the contact number evolution of compression experiments as we vary particle shape. The pair correlation function also shows a different geometric feature with particle shape. Using cyclic compression, we additionally explore the stress relaxation and dynamical heterogeneity of the particles. [Preview Abstract] |
Sunday, November 20, 2016 8:39AM - 8:52AM |
A30.00004: Clogging and Intermittent Flow in a 2D Hopper Kerstin Nordstrom, Emma Thackray We have constructed a quasi-two-dimensional system of bidisperse, millimeter-scale disks with photoelastic properties that make force networks within the material visible. The system is contained in an acrylic box with an adjustable bottom opening. We can approach the clogging transition by adjusting this opening and by adding external forcing to the top of the flowing pile. By placing the system between cross-polarizers, we can obtain high-speed video of this system during flow, and extract intensity signals that can be used to identify and quantify localized, otherwise indeterminate forces. We simultaneously track individual particle motions, which can be used to identify shear transformation zones in the system. We are therefore able to correlate local forces with rearrangements within the system, and characterize the evolution of this interplay on the approach to the clogging transition. [Preview Abstract] |
Sunday, November 20, 2016 8:52AM - 9:05AM |
A30.00005: Characterizing Three Dimensional Granular Materials David Chen, Jonathan Bares, Hu Zheng, Casey Bester, Robert Behringer We use systems of hydrogel particles to determine the microscopic response of 3D granular systems to deformations near jamming. We visualize the particles using a laser scan technique, and we determine the motion of the particles along with their inter-particle forces and contacts from the reconstructed scans. We focus on their response to shear with low friction. [Preview Abstract] |
Sunday, November 20, 2016 9:05AM - 9:18AM |
A30.00006: Couette shear of an ideal 2D photo-elastic granular system Robert Behringer, Hu Zheng, Jonathan Barés, Dong Wang In this study, Couette shear experiments are conducted using 2D photoelastic granular particles, which allows us to apply infinite shear strain to the granular system. We obtain force information at the granular scale using the calibrated photo-elastic grain force response. The whole granular system is density matched in salt solution, which guarantees an ideal 2D system without basal friction between the particles and the table. The viscosity is negligible at the very small shear strain rate (0.017 rpm). This talk will address two main points: i) how does the system reach a jammed state; ii) how does system reach a long term stable state and what are the properties of that state. [Preview Abstract] |
Sunday, November 20, 2016 9:18AM - 9:31AM |
A30.00007: Slip-stick excitation and travelling waves excite silo honking Nathalie Vriend, Kasia Warburton, Elze Porte Industrial storage silos filled with PET-particles can create a sound upon discharge. The sound forms a nuisance for the environment when the structure starts to act as a loudspeaker and may ultimately result in structural failure. This work investigates the phenomenon experimentally---the deployment of a microphone, an accelerometer and high-speed imaging on a laboratory set-up reveal the driving mechanism for the structural resonance: stick-slip at the wall. Particle image velocimetry shows an asymmetric, upwards travelling wave (at 50 m/s) which contains the dynamic “slip”-region. The frequency of the mechanical motion of the grains is successfully correlated to the frequency of the emitted sound. Friction models are explored to describe and quantify the frictional interaction between the grains and the wall. [Preview Abstract] |
Sunday, November 20, 2016 9:31AM - 9:44AM |
A30.00008: A Fluidic Hourglass Alvaro Marin, Henri Lhuissier, Massimiliano Rossi, Andreas Volk, Christian J. K\"ahler A group of objects passing through a constriction might get eventually stuck. It occurs no matter what type of object is considered: sand in an hourglass, particles in a fluid through a porous medium or people leaving a room in panic. The case of particles in a fluid affects porous mediums, filters and membranes, which become unusable when clogged. Certainly the adherence of the particles to the walls and to each other is an important parameter in such systems (Wyss et al., Phys. Rev. E, 2006), but even without adherence the clogging probability is far from negligible. Focusing in these low-adherence regimes, we use microfluidic devices with a bottleneck of squared cross-section through which we force dilute polystyrene particle solutions with diameters comparable to the bottleneck size and down to one tenth its size. In such low friction conditions we show experimental evidence of a strong transition at a critical particle-to-neck ratio, just as it occurs in dry granular systems (Zuriguel et al., Phys. Rev. E, 2003). We describe analytically such a transition by modeling the arch formation as a purely stochastic process, which yields a good agreement with the experimental data. [Preview Abstract] |
Sunday, November 20, 2016 9:44AM - 9:57AM |
A30.00009: Drag reduction by rotation in granular media. Wonjong Jung, Sung Mok Choi, Wonjung Kim, Ho-Young Kim We present quantitative measurements and mathematical analysis of the granular drag reduction by rotation inspired by some self-burrowing seeds whose morphologies respond to environmental changes in humidity. The seeds create a motion to dig into soil using their moisture-responsive awns, which are basically helical shaped in a dry environment but reversibly deform to a linear shape in a humid environment. When the tip of the awn is fixed by an external support, the hygroscopic deformation of the awn gives the seed a thrust with rotation against the soil. By measuring the granular drag of vertically penetrating intruders with rotation, we find the drag to decrease with its rotation speed. Noting that the relative motions of the grains in contact with the intruder induce the collapse of the force chains in the granular bulk, we develop a general correlation for the drag reduction by rotation in terms of the relative slip velocity of the grains, which successfully explains the drag reduction of the rotating intruders including self-burrowing rotary seeds. [Preview Abstract] |
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