Influence of confinement on granular penetration by impact

Seguin, Antoine; Bertho, Yann; Gondret, Philippe

doi:10.1103/physreve.78.010301

Cited by 118 publications

(114 citation statements)

References 18 publications

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“…The granular material fills the cylindrical container of diameter 19 cm and height 26 cm. The size ratio of the container diameter over the sphere diameter is always larger than 10, so that there is no influence of the radial confinement by the lateral walls of the container neither of the bottom wall [13] as the height of the packing is large. Before each drop, the granular medium is prepared by gently stirring the grains with a thin rod.…”

Section: Methodsmentioning

confidence: 99%

“…Even though their energies are typically many orders of magnitude smaller than those of meteorite impacts, these small scale experiments on granular impacts may be relevant to planetary impact processes, as the progression of crater morphologies as a function of impact energy has been shown to mirror that seen in lunar craters [4]. In these impact experiments, physicists have also been interested in the penetration of the impacting sphere in the granular target [8,9,10,11,12,13,14]. Indeed, despite recent progress on the complex rheology of granular matter [15], the penetration dynamics of a solid sphere into a granular medium is still difficult to understand well as it involves both the complex drag resulting from frictional and collisional processes, and the final stop involving the complex "liquid/solid" transition exhibited by granular matter [16].…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of grain ejection by sphere impact on a granular bed

2009

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The dynamics of grain ejection consecutive to a sphere impacting a granular material is investigated experimentally and the variations of the characteristics of grain ejection with the control parameters are quantitatively studied. The time evolution of the corona formed by the ejected grains is reported, mainly in terms of its diameter and height, and favourably compared with a simple ballistic model. A key characteristic of the granular corona is that the angle formed by its edge with the horizontal granular surface remains constant during the ejection process, which again can be reproduced by the ballistic model. The number and the kinetic energy of the ejected grains is evaluated and allows for the calculation of an effective restitution coefficient characterizing the complex collision process between the impacting sphere and the fine granular target. The effective restitution coefficient is found to be constant when varying the control parameters.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamics of grain ejection by sphere impact on a granular bed

2009

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“…By decreasing transverse wall gap L y from 800d g to 40d g , we observe that the drag force F increases with the confinement ratio d/L y as expected from [13], and that the upstream cluster size λ c also increases. When the sidewalls are close enough(L y /d 10, the front of the cluster is no more curved but perpendicular to the sidewalls and much far from the intruder.…”

Section: Influence Of Sidewallsmentioning

confidence: 50%

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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“…1(a). Note that D C /D 0 = 4.5, which is below the critical ratio of 5 identified by Seguin et al [20]. However, this is fixed for all experiments; thus the context of our analysis and discussion is independent of geometrical influence.…”

Section: Methodsmentioning

confidence: 93%

“…Here φ is the packing fraction and φ c is a critical packing fraction [8] (close to the random close packing limit). Scalings for deeper penetrations generally take the form δ/D 0 ∝ (ρ 0 /ρ g ) β (H/D 0 ) α , where both exponents are found to be dependent on the geometry of the container and, in particular, the container-to-sphere diameter ratio [20]. Recently, the effect of cohesion by mixing glass beads with water was studied [21,22], showing that the penetration depth exhibited a nonmonotonic dependence on the initial moisture content in the granular bed, whereby the cohesion from interparticle liquid bridges can play a dual role of creating a lower bulk density but also more internal friction, depending on the grain size and impact speed.…”

Section: Introductionmentioning

confidence: 99%

Penetration in bimodal, polydisperse granular material

2016

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We investigate the impact penetration of spheres into granular media which are compositions of two discrete size ranges, thus creating a polydisperse bimodal material. We examine the penetration depth as a function of the composition (volume fractions of the respective sizes) and impact speed. Penetration depths were found to vary between δ = 0.5D 0 and δ = 7D 0 , which, for mono-modal media only, could be correlated in terms of the total drop height, H = h + δ, as in previous studies, by incorporating correction factors for the packing fraction. Bimodal data can only be collapsed by deriving a critical packing fraction for each mass fraction. The data for the mixed grains exhibit a surprising lubricating effect, which was most significant when the finest grains , with a size ratio, = d l /d s , larger than 3 and mass fractions over 25%, despite the increased packing fraction. We postulate that the small grains get between the large grains and reduce their intergrain friction, only when their mass fraction is sufficiently large to prevent them from simply rattling in the voids between the large particles. This is supported by our experimental observations of the largest lubrication effect produced by adding small glass beads to a bed of large sand particles with rough surfaces.

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Influence of confinement on granular penetration by impact

Cited by 118 publications

References 18 publications

Dynamics of grain ejection by sphere impact on a granular bed

Dynamics of grain ejection by sphere impact on a granular bed

Dense flow around a sphere moving into a cloud of grains

Penetration in bimodal, polydisperse granular material

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