Dynamic jamming fronts

Waitukaitis, Scott; Roth, Leah K.; Vitelli, Vincenzo; Jaeger, Heinrich M.

doi:10.1209/0295-5075/102/44001

Cited by 62 publications

(75 citation statements)

References 28 publications

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“…The upstream extension of the cluster λ = r c − d/2 is averaged in the small θ range −5 deg < θ < 5 deg around the x-direction of motion. As in one dimensional experiments where a straight rake starts moving [10], we observe that the front position λ moves away linearly in time, with a velocity that is proportional to V 0 and increases with φ 0 . But in contrast to the one-dimensional configuration of [10], this regime is here only transient until a steady regime is reached with a constant value λ c despite some fluctuations (Fig.…”

Section: Flow Results Without Sidewallssupporting

confidence: 69%

“…2). This steady regime appears when the grain flux upstream the intruder is balanced by the grain flux on the intruder sides which can not occur in the one-dimensional configuration of [10] as no grains can circumvent the rake. In the following, we restrict our study to this steady state regime which allows time averaging of the different quantities.…”

Section: Flow Results Without Sidewallsmentioning

confidence: 99%

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Dense flow around a sphere moving into a cloud of grains

et al. 2017

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Abstract. A bidimensional simulation of a sphere moving at constant velocity into a cloud of smaller spherical grains without gravity is presented with a non-smooth contact dynamics method. A dense granular "cluster" zone of about constant solid fraction builds progressively around the moving sphere until a stationary regime appears with a constant upstream cluster size that increases with the initial solid fraction φ 0 of the cloud. A detailed analysis of the local strain rate and local stress fields inside the cluster reveals that, despite different spatial variations of strain and stresses, the local friction coefficient μ appears to depend only on the local inertial number I as well as the local solid fraction φ, which means that a local rheology does exist in the present non parallel flow. The key point is that the spatial variations of I inside the cluster does not depend on the sphere velocity and explore only a small range between about 10 −2 and 10 −1 . The influence of sidewalls is then investigated on the flow and the forces.

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Section: Flow Results Without Sidewallssupporting

confidence: 69%

Section: Flow Results Without Sidewallsmentioning

confidence: 99%

Dense flow around a sphere moving into a cloud of grains

et al. 2017

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“…Using a simple, dry model system of disks, Waitukaitis et al 15 provided a more detailed picture for the basic mechanism of how dynamic jamming fronts can develop. Their 2D system starts in an unjammed configuration, which is then uniaxially compressed, giving rise to a traveling front with a speed which is proportional to the pushing speed and diverges as the packing fraction of the initial, undisturbed state approaches jamming.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we return to the complexity of a dense cornstarch suspension, but with a setup more in the spirit of Waitukaitis et al, 15 i.e., we perform impact experiments using a horizontal floating layer of suspension of thickness h. This quasi two-dimensional geometry enables us to directly visualize the motion of the suspension using high speed imaging. We then compare our optical measurements to the force we measure as the jamming front is propagating and when it hits a boundary.…”

Section: Introductionmentioning

confidence: 99%

Quasi-2D dynamic jamming in cornstarch suspensions: visualization and force measurements

2014

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We report experiments investigating jamming fronts in a floating layer of cornstarch suspension. The suspension has a packing fraction close to jamming, which dynamically turns into a solid when impacted at a high speed. We show that the front propagates in both axial and transverse direction from the point of impact, with a constant ratio between the two directions of propagation of approximately 2. Inside the jammed solid, we observe an additional compression, which results from the increasing stress as the solid grows. During the initial growth of the jammed solid, we measure a force response that can be completely accounted for by added mass. Only once the jamming front reaches a boundary, the added mass cannot account for the measured force anymore. We do not, however, immediately see a strong force response as we would expect when compressing a jammed packing. Instead, we observe a delay in the force response on the pusher, which corresponds to the time it takes for the system to develop a close to uniform velocity gradient that spans the complete system.

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“…Fragility and the incipient nonlinear behavior is a collective phenomenon triggered by the mean global topology of the network that is composed of unbreakable Hookean springs (no smooth deformation can change z; springs must be added or removed). By contrast, in granular media, additional and crucial nonlinearities are typically introduced also at the local level, e.g., by the Hertzian interaction between grains or particle rearrangements that leads to a distinct shock phenomenology (9)(10)(11)(12)(13)(14).…”

mentioning

confidence: 99%

Shear shocks in fragile networks

Ulrich¹,

Upadhyaya²,

Opheusden³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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A minimal model for studying the mechanical properties of amorphous solids is a disordered network of point masses connected by unbreakable springs. At a critical value of its mean connectivity, such a network becomes fragile: it undergoes a rigidity transition signaled by a vanishing shear modulus and transverse sound speed. We investigate analytically and numerically the linear and nonlinear visco-elastic response of these fragile solids by probing how shear fronts propagate through them. Our approach, which we tentatively label shear front rheology, provides an alternative route to standard oscillatory rheology. In the linear regime, we observe at late times a diffusive broadening of the fronts controlled by an effective shear viscosity that diverges at the critical point. No matter how small the microscopic coefficient of dissipation, strongly disordered networks behave as if they were overdamped because energy is irreversibly leaked into diverging nonaffine fluctuations. Close to the transition, the regime of linear response becomes vanishingly small: the tiniest shear strains generate strongly nonlinear shear shock waves qualitatively different from their compressional counterparts in granular media. The inherent nonlinearities trigger an energy cascade from low to high frequency components that keep the network away from attaining the quasistatic limit. This mechanism, reminiscent of acoustic turbulence, causes a superdiffusive broadening of the shock width.high damping materials | nonaffine response | jamming | polymer networks | isostaticity M any natural and manmade amorphous structures ranging from glasses to gels can be modeled as disordered viscoelastic networks of point masses (nodes) connected by springs. Despite its simplicity, the spring network model uncovers the remarkable property that the rigidity of an amorphous structure depends crucially on its mean coordination number z, i.e., the average number of nodes that each node is connected to (1). For an unstressed spring network in D dimensions, the critical coordination number z c = 2D separates two disordered states of matter: above z c the system is rigid, below z c it is floppy. Therefore, z c can be identified as a critical point in the theory of rigidity phase transitions (2-4).Various elastic properties are seen to scale with the control parameter Δz = z − z c > 0, close to the critical point (1). For example, the shear modulus vanishes as a power law of Δz (5-7). At the critical point, the disordered network becomes mechanically fragile in the sense that shear deformations cost no energy within linear elasticity. This property is shared with packings and even chains of Hertzian grains just in contact, which display also a zero bulk modulus (3,8). There is, however, an important difference. In the disordered spring networks, local particle interactions are harmonic. Fragility and the incipient nonlinear behavior is a collective phenomenon triggered by the mean global topology of the network that is composed of unbreakable Hookean springs...

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Dynamic jamming fronts

Cited by 62 publications

References 28 publications

Dense flow around a sphere moving into a cloud of grains

Dense flow around a sphere moving into a cloud of grains

Quasi-2D dynamic jamming in cornstarch suspensions: visualization and force measurements

Shear shocks in fragile networks

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