CiteULike: weeks's jamming

Velocity Profiles in Slowly Sheared Bubble Rafts

John Lauridsen — 2008-03-28T12:36:40-00:00

Physical Review Letters, Vol. 93, No. 1. (2004)

Measurements of average velocity profiles in a bubble raft subjected to slow, steady shear demonstrate the coexistence between a flowing state and a jammed state similar to that observed for three-dimensional foams and emulsions [P. Coussot et al., Phys. Rev. Lett. 88, 218301 (2002)]. For sufficiently slow shear, the flow is generated by nonlinear topological rearrangements. We report on the connection between this short-time motion of the bubbles and the long-time averages. We find that velocity profiles for individual rearrangement events fluctuate, but a smooth, average velocity is reached after averaging over only a relatively few events.

Shear Thickening of Cornstarch Suspensions as a Reentrant Jamming Transition

Abdoulaye Fall — 2008-03-18T01:32:20-00:00

Physical Review Letters, Vol. 100, No. 1. (2008)

We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits shear thickening. From magnetic resonance imaging velocimetry and classical rheology it follows that as a function of the applied stress the suspension is first solid (yield stress), then liquid, and then solid again when it shear thickens. For the onset of thickening we find that the smaller the gap of the shear cell, the lower the shear rate at which thickening occurs. Shear thickening can then be interpreted as the consequence of dilatancy: the system under flow wants to dilate but instead undergoes a jamming transition because it is confined, as confirmed by measurement of the dilation of the suspension as a function of the shear rate.

Universal features of the fluid to solid transition for attractive colloidal particles

V Prasad — 2008-06-30T17:06:24-00:00

Faraday Discussions, Vol. 123 (2003), pp. 1-12.

Attractive colloidal particles can exhibit a fluid to solid phase transition if the magnitude of the attractive interaction is sufficiently large, if the volume fraction is sufficiently high, and if the applied stress is sufficiently small. The nature of this fluid to solid transition is similar for many different colloid systems, and for many different forms of interaction. The jamming phase transition captures the common features of these fluid to solid translations, by unifying the behavior as a function of the particle volume fraction, the energy of interparticle attractions, and the applied stress. This paper describes the applicability of the jamming state diagram, and highlights those regions where the fluid to solid transition is still poorly understood. It also presents new data for gelation of colloidal particles with an attractive depletion interaction, providing more insight into the origin of the fluid to solid transition.

Slow dynamics in glasses, gels and foams

Luca Cipelletti — 2008-04-28T14:27:59-00:00

Current Opinion in Colloid & Interface Science, Vol. 7, No. 3-4. (August 2002), pp. 228-234.

Slow dynamics and aging effects in disordered, out-of-equilibrium systems are a rich and fascinating topic, yet still poorly understood. Recent developments in light scattering methods, such as the multispeckle technique, combined with new theoretical approaches that underline the analogies between different glassy materials are bringing a better understanding of these phenomena.

Jamming Transition in Granular Systems

TS Majmudar — 2007-12-31T21:59:04-00:00

Physical Review Letters, Vol. 98, No. 5. (2007)

Recent simulations have predicted that near jamming for collections of spherical particles, there will be a discontinuous increase in the mean contact number Z at a critical volume fraction c. Above c, Z and the pressure P are predicted to increase as power laws in -c. In experiments using photoelastic disks we corroborate a rapid increase in Z at c and power-law behavior above c for Z and P. Specifically we find a power-law increase as a function of -c for Z-Zc with an exponent around 0.5, and for P with an exponent around 1.1. These exponents are in good agreement with simulations. We also find reasonable agreement with a recent mean-field theory for frictionless particles.

Traffic and related self-driven many-particle systems

Dirk Helbing — 2008-05-19T19:52:16-00:00

Reviews of Modern Physics, Vol. 73, No. 4. (7 December 2001), 1067.

Since the subject of traffic dynamics has captured the interest of physicists, many surprising effects have been revealed and explained. Some of the questions now understood are the following: Why are vehicles sometimes stopped by “phantom traffic jams” even though drivers all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction in the volume of traffic cause a lasting traffic jam? Under which conditions can speed limits speed up traffic? Why do pedestrians moving in opposite directions normally organize into lanes, while similar systems “freeze by heating”? All of these questions have been answered by applying and extending methods from statistical physics and nonlinear dynamics to self-driven many-particle systems. This article considers the empirical data and then reviews the main approaches to modeling pedestrian and vehicle traffic. These include microscopic (particle-based), mesoscopic (gas-kinetic), and macroscopic (fluid-dynamic) models. Attention is also paid to the formulation of a micro-macro link, to aspects of universality, and to other unifying concepts, such as a general modeling framework for self-driven many-particle systems, including spin systems. While the primary focus is upon vehicle and pedestrian traffic, applications to biological or socio-economic systems such as bacterial colonies, flocks of birds, panics, and stock market dynamics are touched upon as well.

Phase transition in a static granular system

Matthias Schröter — 2008-04-21T22:31:55-00:00

EPL (Europhysics Letters), Vol. 78, No. 4. (2007), 44004.

We find that a column of glass beads exhibits a well-defined transition between two phases that differ in their resistance to shear. Pulses of fluidization are used to prepare static sedimented states with well-defined particle volume fractions ph in the range 0.57-0.63. The resistance to shear is determined by slowly inserting a rod into the column of beads. Force measurements and bed height measurements both indicate that the transition occurs at ph = 0.60 for a range of speeds of the rod.

Signatures of Glass Formation in a Fluidized Bed of Hard Spheres

Daniel Goldman — 2008-01-23T18:42:00-00:00

Physical Review Letters, Vol. 96, No. 14. (2006), pp. 145702-145702.

We demonstrate that a fluidized bed of hard spheres during defluidization displays properties associated with formation of a glass. The final state is rate dependent, and as this state is approached, the bed exhibits heterogeneity with increasing time and length scales. The formation of a glass results in the arrest of macroscopic particle motion and thus the loss of fluidization. Microscopic motion persists in this state, but the bed can be jammed by application of a small increase in flow rate. Thus a fluidized bed can serve as a test system for studies of glass formation and jamming.

Sheared foam as a supercooled liquid?

SA Langer — 2007-12-31T22:52:55-00:00

EPL (Europhysics Letters), Vol. 49, No. 1. (2000), pp. 68-74.

We conduct numerical simulations on a simple model of a two-dimensional steady-state sheared foam, and define a quantity G that measures stress fluctuations in the constant-area system. This quantity reduces to the temperature in an equilibrium system. We find that the relation between the viscosity and G is the same as that between viscosity and temperature in a very different system, namely a supercooled liquid. This is the first evidence of a common phenomenon linking these two systems.

Jamming and Fluctuations in Granular Drag

I Albert — 2007-09-27T03:46:04-00:00

Physical Review Letters, Vol. 84, No. 22. (29 May 2000), 5122.

We investigate the dynamic evolution of jamming in granular media through fluctuations in the granular drag force. The successive collapse and formation of jammed states give a stick-slip nature to the fluctuations which is independent of the contact surface between the grains and the dragged object; thus implying that the stress-induced collapse is nucleated in the bulk of the granular sample. We also find that while the fluctuations are periodic at small depths; they become “stepped” at large depths; a transition which we interpret as a consequence of the long-range nature of the force chains.

Nature of the divergence in low shear viscosity of colloidal hard-sphere dispersions

Zhengdong Cheng — 2007-07-11T20:42:14-00:00

Physical Review E, Vol. 65, No. 4. (April 2002), pp. 041405-041405.

Measurements of the low-shear viscosity η o with a Zimm-Crothers viscometer for dispersions of colloidal hard spheres are reported as a function of volume fraction φ up to 0.56. Nonequilibrium theories based on solutions to the two-particle Smoluchoski equation or ideal mode coupling approximations do not capture the divergence. However; the nonhydrodynamic contribution to the relative viscosity Δη o is correlated over a wide range of volume fractions by the Doolittle and Adam-Gibbs equations; indicating an exponential divergence at φ m =0.625±0.015. The data extend the previously proposed master curve; providing a test for improved theories for the many-body thermodynamic and hydrodynamic interactions that determine the viscosity of hard-sphere dispersions.

Jamming of Granular Flow in a Two-Dimensional Hopper

Kiwing To — 2007-09-27T03:12:29-00:00

Physical Review Letters, Vol. 86, No. 1. (1 January 2001), 71.

We study experimentally the jamming phenomenon of granular flow of monodisperse disks of D = 5 mm diameter in a two-dimensional hopper with opening R . The jamming probability J ( d ) is measured where d ≡ R / D . We found that J ( d ) decreases from 1 to zero when d increases from 2 to 5. From observing the disk configurations of the arch in the jamming events; the jamming probability can be explained quantitatively by treating the arch as the trajectory of a restricted random walker.

Reply to `Comment on “Jamming at zero temperature and zero applied stress: The epitome of disorder” '

Corey O'Hern — 2007-09-27T03:05:03-00:00

Physical Review E, Vol. 70, No. 4. (2004), pp. 043302-043302.

We answer the questions raised by Donev, Torquato, Stillinger, and Connelly (DTSC) in their preceding Comment on "Jamming at zero temperature and zero applied stress: The epitome of disorder" [Phys. Rev. E 70, 043301 (2004)] We emphasize that we follow a fundamentally different approach than they have done to reinterpret random close packing in terms of the "maximally random jammed" framework. We define the "maximally random jammed packing fraction" to be where the largest number of initial states, chosen completely randomly, have relaxed final states at the jamming threshold in the thermodynamic limit. Thus, we focus on an ensemble of states at the jamming threshold, while DTSC are interested in determining the amount of order and degree of jamming for a particular configuration. We also argue that soft-particle systems are as "clean" as those using hard spheres for studying jammed packings and point out the benefits of using soft potentials.

Comment on `Jamming at zero temperature and zero applied stress: The epitome of disorder'

Aleksandar Donev — 2007-09-27T03:04:22-00:00

Physical Review E, Vol. 70, No. 4. (2004), pp. 043301-043301.

O'Hern, Silbert, Liu, and Nagel [Phys. Rev. E. 68, 011306 (2003)] claim that a special point J of a "jamming phase diagram" (in density, temperature, stress space) is related to random close packing of hard spheres and that it represents, for their suggested definitions of jammed and random, the recently introduced maximally random jammed state. We point out several difficulties with their definitions and question some of their claims. Furthermore, we discuss the connections between their algorithm and other hard-sphere packing algorithms in the literature.

Jamming, Two-Fluid Behavior, and “Self-Filtration” in Concentrated Particulate Suspensions

MD Haw — 2007-09-22T19:54:19-00:00

Physical Review Letters, Vol. 92, No. 18. (2004), pp. 185506-185506.

We study the flow of model hard-sphere colloidal suspensions at high volume fraction driven through a constriction by a pressure gradient. Above a particle-size dependent limit 0, direct microscopic observations demonstrate jamming and unjamming—conversion of fluid to solid and vice versa—during flow. We show that such a jamming flow produces a reduction in colloid concentration x downstream of the constriction. We propose that this "self-filtration" effect is due to a combination of jamming of the particulate part of the system and continuing flow of the liquid part, i.e., the solvent, through the pores of the jammed solid. Thus we link jamming in colloidal and granular media with a "two-fluid-like" picture of the flow of concentrated suspensions. Results are also discussed in the light of the original experiments of Reynolds on dilation in granular materials.

Effective Temperatures of a Driven System Near Jamming

Ian Ono — 2007-09-22T19:05:42-00:00

Physical Review Letters, Vol. 89, No. 9. (2002), 095703.

Fluctuations in a model of a sheared; zero-temperature foam are studied numerically. Five different quantities that independently reduce to the true temperature in an equilibrium thermal system are calculated. One of the quantities is calculated up to an unknown coefficient. The other four quantities have the same value and all five have the same shear-rate dependence. These results imply that statistical mechanics is useful for the system even though it is far from thermal equilibrium.

Force Distributions near Jamming and Glass Transitions

Corey O'Hern — 2007-05-18T10:36:37-00:00

Physical Review Letters, Vol. 86, No. 1. (1 January 2001), 111.

We calculate the distribution of interparticle normal forces P ( F ) near the glass and jamming transitions in model supercooled liquids and foams; respectively. P ( F ) develops a peak that appears near the glass or jamming transitions; whose height increases with decreasing temperature; decreasing shear stress and increasing packing density. A similar shape of P ( F ) was observed in experiments on static granular packings. We propose that the appearance of this peak signals the development of a yield stress. The sensitivity of the peak to temperature; shear stress; and density lends credence to the recently proposed generalized jamming phase diagram.

Jamming at zero temperature and zero applied stress: The epitome of disorder

Corey O'Hern — 2007-09-21T04:00:05-00:00

Physical Review E, Vol. 68, No. 1. (25 July 2003), pp. 011306-011306.

We have studied how two- and three-dimensional systems made up of particles interacting with finite range; repulsive potentials jam (i.e.; develop a yield stress in a disordered state) at zero temperature and zero applied stress. At low packing fractions φ; the system is not jammed and each particle can move without impediment from its neighbors. For each configuration; there is a unique jamming threshold φ c at which particles can no longer avoid each other; and the bulk and shear moduli simultaneously become nonzero. The distribution of φ c values becomes narrower as the system size increases; so that essentially all configurations jam at the same packing fraction in the thermodynamic limit. This packing fraction corresponds to the previously measured value for random close packing. In fact; our results provide a well-defined meaning for “random close packing” in terms of the fraction of all phase space with inherent structures that jam. The jamming threshold; point J ; occurring at zero temperature and applied stress and at the random-close-packing density; has properties reminiscent of an ordinary critical point. As point J is approached from higher packing fractions; power-law scaling is found for the divergence of the first peak in the pair correlation function and in the vanishing of the pressure; shear modulus; and excess number of overlapping neighbors. Moreover; near point J ; certain quantities no longer self-average; suggesting the existence of a length scale that diverges at J . However; point J also differs from an ordinary critical point: the scaling exponents do not depend on dimension but do depend on the interparticle potential. Finally; as point J is approached from high packing fractions; the density of vibrational states develops a large excess of low-frequency modes. Indeed; at point J ; the density of states is a constant all the way down to zero frequency. All of these results suggest that point J is a point of maximal disorder and may control behavior in its vicinity—perhaps even at the glass transition.

Jamming and rheology: an introduction

AJ Liu — 2007-09-21T03:39:42-00:00

(2001), pp. 1-10.

Experimental studies of the flow of concentrated hard sphere suspensions into a constriction

L Isa — 2006-06-07T11:46:33-00:00

Journal of Physics: Conference Series, Vol. 40, No. 1. (2006), pp. 124-132.

Interesting flow properties are observed when a concentrated suspension of colloidal particles flows into a geometrical constriction. We present here a description of two different experimental techniques used to study the pressure driven flow of dense suspensions of micron-sized hard spheres into glass capillaries. The first one involves the analysis of the driving pressure during the flow, the other one is based on fast confocal microscopy. Technical details are given, together with a selection of preliminary results.

Multiscaling at Point J: Jamming is a Critical Phenomenon

JA Drocco — 2007-08-21T21:39:30-00:00

Physical Review Letters, Vol. 95, No. 8. (2005)

We analyze the jamming transition that occurs as a function of increasing packing density in a disordered two-dimensional assembly of disks at zero temperature for “Point J” of the recently proposed jamming phase diagram. We measure the total number of moving disks and the transverse length of the moving region, and find a power law divergence as the packing density increases toward a critical jamming density. This provides evidence that the $T=0$ jamming transition as a function of packing density is a second order phase transition. Additionally, we find evidence for multiscaling, indicating the importance of long tails in the velocity fluctuations.

Critical Scaling in Linear Response of Frictionless Granular Packings near Jamming

Wouter Ellenbroek — 2007-09-19T16:52:23-00:00

Physical Review Letters, Vol. 97, No. 25. (2006)

We study the origin of the scaling behavior in frictionless granular media above the jamming transition by analyzing their linear response. The response to local forcing is non-self-averaging and fluctuates over a length scale that diverges at the jamming transition. The response to global forcing becomes increasingly nonaffine near the jamming transition. This is due to the proximity of floppy modes, the influence of which we characterize by the local linear response. We show that the local response also governs the anomalous scaling of elastic constants and contact number.

Is Random Close Packing of Spheres Well Defined?

S Torquato — 2007-09-19T16:41:03-00:00

Physical Review Letters, Vol. 84, No. 10. (6 March 2000), pp. 2064-2067.

Despite its long history; there are many fundamental issues concerning random packings of spheres that remain elusive; including a precise definition of random close packing (RCP). We argue that the current picture of RCP cannot be made mathematically precise and support this conclusion via a molecular dynamics study of hard spheres using the Lubachevsky-Stillinger compression algorithm. We suggest that this impasse can be broken by introducing the new concept of a maximally random jammed state; which can be made precise.

The glass paradigm for colloidal glasses, gels, and other arrested states driven by attractive interactions

Kenneth Dawson — 2005-08-22T03:47:16-00:00

Curr. Opin. Colloid Interface Sci., Vol. 7 (2002), pp. 218-227.

For some time, there has existed the idea that dense colloidal systems with repulsive interactions can be interpreted using certain approaches to glass theory. Recent advances in understanding the role of short-ranged attractive interactions in driving another type of `glass-transition' have considerably extended the range of potential applications for such systems. Within this framework, particle gels are now regarded as `attractive' glasses, and for some concentration regimes the details of the density correlation as we approach gellation for a broad range of experimental systems seem to be well described by glass-transition ideas and laws. Initial suggestions that this might be so came from theory, but the close collaboration between theory, simulation, and experimental science has been mutually stimulating. New advances in the theory are now to be expected, and novel systems where the ideas might be applicable are emerging. The exploration of these ideas is still at the beginning, but there is a reasonable expectation that the glass paradigm will be more generally useful in many areas of soft matter and colloid science, perhaps gathering apparently disparate phenomena of particle gellation, polymer gellation, aggregation, and other aspects of `solidification' into a common interpretive scheme. 2002 Elsevier Scienc Ltd. All rights reserved.

Jamming phase diagram for attractive particles

V Trappe — 2006-09-13T15:26:10-00:00

Nature, Vol. 411, No. 6839. (14 June 2001), pp. 772-775.

A wide variety of systems, including granular media, colloidal suspensions and molecular systems, exhibit non-equilibrium transitions from a fluid-like to a solid-like state, characterized solely by the sudden arrest of their dynamics. Crowding or jamming of the constituent particles traps them kinetically, precluding further exploration of the phase space1. The disordered fluid-like structure remains essentially unchanged at the transition. The jammed solid can be refluidized by thermalization, through temperature or vibration, or by an applied stress. The generality of the jamming transition led to the proposal2 of a unifying description, based on a jamming phase diagram. It was further postulated that attractive interactions might have the same effect in jamming the system as a confining pressure, and thus could be incorporated into the generalized description. Here we study experimentally the fluid-to-solid transition of weakly attractive colloidal particles, which undergo markedly similar gelation behaviour with increasing concentration and decreasing thermalization or stress. Our results support the concept of a jamming phase diagram for attractive colloidal particles, providing a unifying link between the glass transition3, gelation4, 5 and aggregation6, 7, 8.

Jamming is not just cool any more

Andrea Liu — 2007-05-18T10:34:26-00:00

Nature, Vol. 396, No. 6706. (5 November 1998), pp. 21-22.