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Sun Y, Wang C, Yang J, Shi W, Pang Q, Wang Y, Li J, Hu B, Xia C. Evident structural anisotropies arising from near-zero particle asphericity in granular spherocylinder packings. Phys Rev E 2024; 110:014903. [PMID: 39161035 DOI: 10.1103/physreve.110.014903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 07/02/2024] [Indexed: 08/21/2024]
Abstract
With magnetic resonance imaging experiments, we study packings of granular spherocylinders with merely 2% asphericity. Evident structural anisotropies across all length scales are identified. Most interestingly, the global nematic order decreases with increasing packing fraction, while the local contact anisotropy shows an opposing trend. We attribute this counterintuitive phenomenon to a competition between gravity-driven ordering aided by frictional contacts and a geometric frustration effect at the marginally jammed state. It is also surprising to notice that such slight particle asphericity can trigger non-negligible correlations between contact-level and mesoscale structures, manifested in drastically different nonaffine structural rearrangements upon compaction from that of granular spheres. These observations can help improve statistical mechanical models for the orientational order transformation of nonspherical granular particle packings, which involves complex interplays between particle shape, frictional contacts, and external force field.
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Affiliation(s)
| | | | | | | | | | - Yujie Wang
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China
- Department of Physics, College of Mathematics and Physics, Chengdu University of Technology, Chengdu 610059, China
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2
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Berzi D, Buettner KE, Curtis JS. Dense shearing flows of soft, frictional cylinders. SOFT MATTER 2021; 18:80-88. [PMID: 34849518 DOI: 10.1039/d1sm01395e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We perform discrete numerical simulations at a constant volume of dense, steady, homogeneous flows of true cylinders interacting via Hertzian contacts, with and without friction, in the absence of preferential alignment. We determine the critical values of the solid volume fraction and the average number of contacts per particle above which rate-independent components of the stresses develop, along with a sharp increase in the fluctuations of angular velocity. We show that kinetic theory, extended to account for a velocity correlation at solid volume fractions larger than 0.49, can quantitatively predict the measured fluctuations of translational velocity, at least for sufficiently rigid cylinders, for any value of the cylinder aspect ratio and friction investigated here. The measured pressure above and below the critical solid volume fraction is in agreement with a recent theory originally intended for spheres that conjugates extended kinetic theory, the finite duration of collisions between soft particles and the development of an elastic network of long-lasting contacts responsible for the rate-independency of the flows in the supercritical regime. Finally, we find that, for sufficiently rigid cylinders, the ratio of shear stress to pressure in the subcritical regime is a linear function of the ratio of the shear rate to a suitable measure of the fluctuations of translational velocity, in qualitative accordance with kinetic theory, with an intercept that increases with friction. A decrease in the particle stiffness gives rise to nonlinear effects that greatly diminishes the stress ratio.
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Affiliation(s)
| | - Kevin E Buettner
- University of Florida, 32611 Gainesville, FL, USA
- ExxonMobil Research and Engineering, 77389 Spring, TX, USA
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3
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Berry N, Zhang Y, Haeri S. Lees-Edwards boundary conditions for the multi-sphere discrete element method. POWDER TECHNOL 2021. [DOI: 10.1016/j.powtec.2021.05.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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4
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Jiang X, Matsushima T, Blumenfeld R. Structural characteristics of ordered clusters in packs of ellipses. EPJ WEB OF CONFERENCES 2021. [DOI: 10.1051/epjconf/202124906004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Structural characteristics of two-dimensional elliptic granular packs with various aspect ratios and intergranular friction coefficients were studied using the Discrete Element Method (DEM). Isotropic compaction from random unjammed state leads to a jammed state with polycrystals of orientationally ordered clusters (OOC). The OOCs were identified using a cluster labelling algorithm, based on the relative angle Δθ between the major axes of two contacting particles. The threshold value of Δθ was optimised to give the strongest correlation between OOCs and the force chain network. We found that the resulting OOC size distribution decays algebraically with an exponent of −2, independently of grain aspect ratio and material properties.
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5
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Dong J, Trulsson M. Transition from steady shear to oscillatory shear rheology of dense suspensions. Phys Rev E 2020; 102:052605. [PMID: 33327063 DOI: 10.1103/physreve.102.052605] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 10/20/2020] [Indexed: 11/07/2022]
Abstract
Recent studies have highlighted that oscillatory and time-dependent shear flows might help increase the flowability of dense suspensions. While most focus has been on cross-flows we here study a simple two-dimensional suspensions where we apply simultaneously oscillatory and stationary shear along the same direction. We first show that the dissipative viscosities in this set-up significantly decrease with an increasing shear-rate magnitude of the oscillations and given that the oscillatory strain is small, in a similar fashion as found previously for cross-flow oscillations. As for cross-flow oscillations, the decrease can be attributed to the large decrease in the number of contacts and an altered microstructure as one transitions from a steady shear to an oscillatory shear dominated rheology. As subresults we find both an extension to the μ(J) rheology, a constitutive relationship between the shear stresses and the shear rate, valid for oscillatory shear flows and that shear-jamming of frictional particles at oscillatory shear dominated flows occurs at higher packing fractions compared to steady shear dominated flows.
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Affiliation(s)
- Junhao Dong
- Theoretical Chemistry, Lund University, 221 00 Lund, Sweden
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6
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Keta YE, Olsson P. Translational and rotational velocities in shear-driven jamming of ellipsoidal particles. Phys Rev E 2020; 102:052905. [PMID: 33327139 DOI: 10.1103/physreve.102.052905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 11/05/2020] [Indexed: 06/12/2023]
Abstract
We study shear-driven jamming of ellipsoidal particles at zero temperature with a focus on the microscopic dynamics. We find that a change from spherical particles to ellipsoids with aspect ratio α=1.02 gives dramatic changes of the microscopic dynamics with much lower translational velocities and a new role for the rotations. Whereas the velocity difference at contacts-and thereby the dissipation-in collections of spheres is dominated by the translational velocities and reduced by the rotations, the same quantity is in collections of ellipsoids instead totally dominated by the rotational velocities. By also examining the effect of different aspect ratios we find that the examined quantities show either a peak or a change in slope at α≈1.2, which thus gives evidence for a crossover between different regions of low and high aspect ratio.
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Affiliation(s)
- Yann-Edwin Keta
- Department of Physics, Umeå University, 901 87 Umeå, Sweden
- Département de Physique, École Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France
- Département de Physique, Université Claude Bernard Lyon 1, 69622 Villeurbanne Cedex, France
| | - Peter Olsson
- Department of Physics, Umeå University, 901 87 Umeå, Sweden
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7
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Marschall TA, Teitel S. Depletion forces in athermally sheared mixtures of frictionless disks and rods in two dimensions. Phys Rev E 2020; 102:042908. [PMID: 33212568 DOI: 10.1103/physreve.102.042908] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 10/01/2020] [Indexed: 11/07/2022]
Abstract
We carry out numerical simulations to study the behavior of an athermal mixture of frictionless circular disks and elongated rods in two dimensions, under three different types of global linear deformation at a finite strain rate: (i) simple shearing, (ii) pure shearing, and (iii) isotropic compression. We find that the fluctuations induced by such deformations lead to depletion forces that cause rods to group in parallel oriented clusters for the cases of simple and pure shear, but not for isotropic compression. For simple shearing, we find that as the fraction of rods increases, this clustering increases, leading to an increase in the average rate of rotation of the rods, and a decrease in the magnitude of their nematic ordering.
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Affiliation(s)
- Theodore A Marschall
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - S Teitel
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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8
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Lebovka NI, Vygornitskii NV, Tarasevich YY. Random sequential adsorption of partially ordered discorectangles onto a continuous plane. Phys Rev E 2020; 102:022133. [PMID: 32942432 DOI: 10.1103/physreve.102.022133] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 08/06/2020] [Indexed: 06/11/2023]
Abstract
A computer simulation was used to study the random sequential adsorption of identical discorectangles onto a continuous plane. The problem was analyzed for a wide range of discorectangle aspect ratios (ɛ∈[1;100]). We studied the anisotropic deposition, i.e., the orientations of the deposited particles were uniformly distributed within some interval such that the particles were preferentially aligned along a given direction. The kinetics of the changes in the packing fraction found at different values of such the alignment are discussed. Partial ordering of the discorectangles significantly affected the packing fraction at the jamming state, φ_{j}, and shifted the cusps in the φ_{j}(ɛ) dependencies. The structure of the jammed state was analyzed using the adsorption of disks of different diameters into the porous space between the deposited discorectangles. The analysis of the connectivity between the discorectangles was performed assuming a core-shell structure of particles.
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Affiliation(s)
- Nikolai I Lebovka
- Department of Physical Chemistry of Disperse Minerals, F. D. Ovcharenko Institute of Biocolloidal Chemistry, NAS of Ukraine, Kyiv 03142, Ukraine
- Department of Physics, Taras Shevchenko Kyiv National University, Kyiv 01033, Ukraine
| | - Nikolai V Vygornitskii
- Department of Physical Chemistry of Disperse Minerals, F. D. Ovcharenko Institute of Biocolloidal Chemistry, NAS of Ukraine, Kyiv 03142, Ukraine
| | - Yuri Yu Tarasevich
- Laboratory of Mathematical Modeling, Astrakhan State University, Astrakhan 414056, Russia
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9
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Mizani S, Gurin P, Aliabadi R, Salehi H, Varga S. Demixing and tetratic ordering in some binary mixtures of hard superellipses. J Chem Phys 2020; 153:034501. [PMID: 32716200 DOI: 10.1063/5.0009705] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We examine the fluid phase behavior of binary mixtures of hard superellipses using the scaled particle theory. The superellipse is a general two-dimensional convex object that can be tuned between the elliptical and rectangular shapes continuously at a given aspect ratio. We find that the shape of the particle affects strongly the stability of isotropic, nematic, and tetratic phases in the mixture even if the side lengths of both species are fixed. While the isotropic-isotropic demixing transition can be ruled out using the scaled particle theory, the first order isotropic-nematic and the nematic-nematic demixing transition can be stabilized with strong fractionation between the components. It is observed that the demixing tendency is strongest in small rectangle-large ellipse mixtures. Interestingly, it is possible to stabilize the tetratic order at lower densities in the mixture of hard squares and rectangles where the long rectangles form a nematic phase, while the squares stay in the tetratic order.
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Affiliation(s)
- Sakine Mizani
- Department of Physics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Péter Gurin
- Institute of Physics and Mechatronics, University of Pannonia, P.O. Box 158, Veszprém H-8201, Hungary
| | - Roohollah Aliabadi
- Department of Physics, Faculty of Science, Fasa University, 74617-81189 Fasa, Iran
| | - Hamdollah Salehi
- Department of Physics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Szabolcs Varga
- Institute of Physics and Mechatronics, University of Pannonia, P.O. Box 158, Veszprém H-8201, Hungary
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10
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Yuan Y, Deng W, Li S. Structural universality in disordered packings with size and shape polydispersity. SOFT MATTER 2020; 16:4528-4539. [PMID: 32356543 DOI: 10.1039/d0sm00110d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We numerically investigate disordered jammed packings with both size and shape polydispersity, using frictionless superellipsoidal particles. We implement the set Voronoi tessellation technique to evaluate the local specific volume, i.e., the ratio of cell volume over particle volume, for each individual particle. We focus on the average structural properties for different types of particles binned by their sizes and shapes. We generalize the basic observation that the larger particles are locally packed more densely than the smaller ones in a polydisperse-sized packing into systems with coupled particle shape dispersity. For this purpose, we define the normalized free volume vf to measure the local compactness of a particle and study its dependency on the normalized particle size A. The definition of vf relies on the calibrated monodisperse specific volume for a certain particle shape. For packings with shape dispersity, we apply the previously introduced concept of equivalent diameter for a non-spherical particle to define A properly. We consider three systems: (A) linear superposition states of mixed-shape packings, (B) merely polydisperse-sized packings, and (C) packings with coupled size and shape polydispersity. For (A), the packing is simply considered as a mixture of different subsystems corresponding to monodisperse packings for different shape components, leading to A = 1, and vf = 1 by definition. We propose a concise model to estimate the shape-dependent factor αc, which defines the equivalent diameter for a certain particle. For (B), vf collapses as a function of A, independent of specific particle shape and size polydispersity. Such structural universality is further validated by a mean-field approximation. For (C), we find that the master curve vf(A) is preserved when particles possess similar αc in a packing. Otherwise, the dispersity of αc among different particles causes the deviation from vf(A). These findings show that a polydisperse packing can be estimated as the combination of various building blocks, i.e., bin components, with a universal relation vf(A).
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Affiliation(s)
- Ye Yuan
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
| | - Wei Deng
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
| | - Shuixiang Li
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
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11
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Marschall TA, Teitel S. Shear-driven flow of athermal, frictionless, spherocylinder suspensions in two dimensions: Spatial structure and correlations. Phys Rev E 2020; 101:032907. [PMID: 32289919 DOI: 10.1103/physreve.101.032907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 02/29/2020] [Indexed: 06/11/2023]
Abstract
We use numerical simulations to study the flow of athermal, frictionless, soft-core two-dimensional spherocylinders driven by a uniform steady-state simple shear applied at a fixed volume and a fixed finite strain rate γ[over ̇]. Energy dissipation is via a viscous drag with respect to a uniformly sheared host fluid, giving a simple model for flow in a non-Brownian suspension with Newtonian rheology. We study the resulting spatial structure of the sheared system, and compute correlation functions of the velocity, the particle density, the nematic order parameter, and the particle angular velocity. Correlations of density, nematic order, and angular velocity are shown to be short ranged both below and above jamming. We compare a system of size-bidisperse particles with a system of size-monodisperse particles, and argue how differences in spatial order as the packing increases lead to differences in the global nematic order parameter. We consider the effect of shearing on initially well ordered configurations, and show that in many cases the shearing acts to destroy the order, leading to the same steady-state ensemble as found when starting from random initial configurations.
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Affiliation(s)
- Theodore A Marschall
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - S Teitel
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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12
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Marschall TA, Van Hoesen D, Teitel S. Shear-driven flow of athermal, frictionless, spherocylinder suspensions in two dimensions: Particle rotations and orientational ordering. Phys Rev E 2020; 101:032901. [PMID: 32290000 DOI: 10.1103/physreve.101.032901] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 02/15/2020] [Indexed: 06/11/2023]
Abstract
We use numerical simulations to study the flow of a bidisperse mixture of athermal, frictionless, soft-core two-dimensional spherocylinders driven by a uniform steady-state simple shear applied at a fixed volume and a fixed finite strain rate γ[over ̇]. Energy dissipation is via a viscous drag with respect to a uniformly sheared host fluid, giving a simple model for flow in a non-Brownian suspension with Newtonian rheology. Considering a range of packing fractions ϕ and particle asphericities α at small γ[over ̇], we study the angular rotation θ[over ̇]_{i} and the nematic orientational ordering S_{2} of the particles induced by the shear flow, finding a nonmonotonic behavior as the packing ϕ is varied. We interpret this nonmonotonic behavior as a crossover from dilute systems at small ϕ, where single-particle-like behavior occurs, to dense systems at large ϕ, where the geometry of the dense packing dominates and a random Poisson-like process for particle rotations results. We also argue that the finite nematic ordering S_{2} is a consequence of the shearing serving as an ordering field, rather than a result of long-range cooperative behavior among the particles. We arrive at these conclusions by consideration of (i) the distribution of waiting times for a particle to rotate by π, (ii) the behavior of the system under pure, as compared to simple, shearing, (iii) the relaxation of the nematic order parameter S_{2} when perturbed away from the steady state, and (iv) by construction, a numerical mean-field model for the rotational motion of a particle. Our results also help to explain the singular behavior observed when taking the α→0 limit approaching circular disks.
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Affiliation(s)
- Theodore A Marschall
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Daniel Van Hoesen
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - S Teitel
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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13
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Nath T, Heussinger C. Rheology in dense assemblies of spherocylinders: Frictional vs. frictionless. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:157. [PMID: 31863209 DOI: 10.1140/epje/i2019-11925-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 12/03/2019] [Indexed: 06/10/2023]
Abstract
Using molecular dynamics simulations, we study the steady shear flow of dense assemblies of anisotropic spherocylindrical particles of varying aspect ratios. Comparing frictionless and frictional particles we discuss the specific role of frictional inter-particle forces for the rheological properties of the system. In the frictional system we evidence a shear-thickening regime, similar to that for spherical particles. Furthermore, friction suppresses the alignment of the spherocylinders along the flow direction. Finally, the jamming density in frictional systems is rather insensitive to variations in aspect ratio, quite contrary to what is known from frictionless systems.
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Affiliation(s)
- Trisha Nath
- Institute for Theoretical Physics, Georg-August University of Göttingen, Friedrich-Hund Platz 1, 37077, Göttingen, Germany
| | - Claus Heussinger
- Institute for Theoretical Physics, Georg-August University of Göttingen, Friedrich-Hund Platz 1, 37077, Göttingen, Germany.
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14
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Yuan Y, VanderWerf K, Shattuck MD, O'Hern CS. Jammed packings of 3D superellipsoids with tunable packing fraction, coordination number, and ordering. SOFT MATTER 2019; 15:9751-9761. [PMID: 31742301 PMCID: PMC6902436 DOI: 10.1039/c9sm01932d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
We carry out numerical studies of static packings of frictionless superellipsoidal particles in three spatial dimensions. We consider more than 200 different particle shapes by varying the three shape parameters that define superellipsoids. We characterize the structural and mechanical properties of both disordered and ordered packings using two packing-generation protocols. We perform athermal quasi-static compression simulations starting from either random, dilute configurations (Protocol 1) or thermalized, dense configurations (Protocol 2), which allows us to tune the orientational order of the packings. In general, we find that superellipsoid packings are hypostatic, with coordination number zJ < ziso, where ziso = 2df and df = 5 or 6 depending on whether the particles are axi-symmetric or not. Over the full range of orientational order, we find that the number of quartic modes of the dynamical matrix for the packings always matches the number of missing contacts relative to the isostatic value. This result suggests that there are no mechanically redundant contacts for ordered, yet hypostatic packings of superellipsoidal particles. Additionally, we find that the packing fraction at jamming onset for disordered packings of superellipsoidal depends on at least two particle shape parameters, e.g. the asphericity A and reduced aspect ratio β of the particles.
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Affiliation(s)
- Ye Yuan
- Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China. and Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA
| | - Kyle VanderWerf
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Mark D Shattuck
- Benjamin Levich Institute and Physics Department, The City College of New York, New York, New York 10031, USA
| | - Corey S O'Hern
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA and Department of Physics, Yale University, New Haven, Connecticut 06520, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA and Graduate Program in Computational Biology and Bioinformatics, Yale University, New Haven, Connecticut 06520, USA
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15
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Peshkov A, Girvan M, Richardson DC, Losert W. Reversibility of granular rotations and translations. Phys Rev E 2019; 100:042905. [PMID: 31771010 DOI: 10.1103/physreve.100.042905] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Indexed: 06/10/2023]
Abstract
We analyze reversibility of displacements and rotations of spherical grains in three-dimensional compression experiments. Using transparent acrylic beads with cylindrical holes and index matching techniques, we are not only capable of tracking displacements but also analyzing reversibility of rotations. We observe that for moderate compression amplitudes, up to one bead diameter, the translational displacements of the beads after each cycle become mostly reversible after an initial transient. By contrast, granular rotations are largely irreversible. We find a weak correlation between translational and rotational displacements, indicating that rotational reversibility depends on more subtle changes in contact distributions and contact forces between grains compared with displacement reversibility. Three-dimensional rotations in dense granular systems are particularly important, since frictional losses associated with rotations are the dominant mechanism for energy dissipation. As such our work provides a first step toward a thorough study of rotations and tangential forces to understand the granular dynamics in dense systems.
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Affiliation(s)
- Anton Peshkov
- IREAP, University of Maryland, College Park, Maryland 20742, USA
| | - Michelle Girvan
- Department of Physics, IPST and IREAP, University of Maryland, College Park, Maryland 20742, USA
| | - Derek C Richardson
- Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA
| | - Wolfgang Losert
- Department of Physics, IPST and IREAP, University of Maryland, College Park, Maryland 20742, USA
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16
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Marschall TA, Teitel S. Shear-driven flow of athermal, frictionless, spherocylinder suspensions in two dimensions: Stress, jamming, and contacts. Phys Rev E 2019; 100:032906. [PMID: 31639991 DOI: 10.1103/physreve.100.032906] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Indexed: 06/10/2023]
Abstract
We use numerical simulations to study the flow of a bidisperse mixture of athermal, frictionless, soft-core two-dimensional spherocylinders driven by a uniform steady-state shear strain applied at a fixed finite rate. Energy dissipation occurs via a viscous drag with respect to a uniformly sheared host fluid, giving a simple model for flow in a non-Brownian suspension and resulting in a Newtonian rheology. We study the resulting pressure p and deviatoric shear stress σ of the interacting spherocylinders as a function of packing fraction ϕ, strain rate γ[over ̇], and a parameter α that measures the asphericity of the particles; α is varied to consider the range from nearly circular disks to elongated rods. We consider the direction of anisotropy of the stress tensor, the macroscopic friction μ=σ/p, and the divergence of the transport coefficient η_{p}=p/γ[over ̇] as ϕ is increased to the jamming transition ϕ_{J}. From a phenomenological analysis of Herschel-Bulkley rheology above jamming, we estimate ϕ_{J} as a function of asphericity α and show that the variation of ϕ_{J} with α is the main cause for differences in rheology as α is varied; when plotted as ϕ/ϕ_{J}, rheological curves for different α qualitatively agree. However, a detailed scaling analysis of the divergence of η_{p} for our most elongated particles suggests that the jamming transition of spherocylinders may be in a different universality class than that of circular disks. We also compute the number of contacts per particle Z in the system and show that the value at jamming Z_{J} is a nonmonotonic function of α that is always smaller than the isostatic value. We measure the probability distribution of contacts per unit surface length P(ϑ) at polar angle ϑ with respect to the spherocylinder spine and find that as α→0 this distribution seems to diverge at ϑ=π/2, giving a finite limiting probability for contacts on the vanishingly small flat sides of the spherocylinder. Finally, we consider the variation of the average contact force as a function of location on the particle surface.
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Affiliation(s)
- Theodore A Marschall
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - S Teitel
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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