Birth and growth of a granular jet

Royer, J; Corwin, Eric I.; Conyers, Bryan; Flior, Andrew; Rivers, Mark L.; Eng, Peter J.; Jaeger, Heinrich M.

doi:10.1103/physreve.78.011305

Cited by 30 publications

(52 citation statements)

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“…For fine powders in air, granular jets and cavity collapse occur during impact [12,13]. Subsequent studies showed that the ambient pressure of the interstitial fluid (air) is an important element for the observed fluid-like behavior [14][15][16], while for denser packing the impact penetration is much reduced [17]. However, the question of the physical mechanisms and control parameters that give rise to such a wide variety of phenomena is still largely open.…”

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confidence: 99%

Unifying Impacts in Granular Matter from Quicksand to Cornstarch

2016

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A sharp transition between liquefaction and transient solidification is observed during impact on a granular suspension depending on the initial packing fraction. We demonstrate, via high-speed pressure measurements and a two-phase modeling, that this transition is controlled by a coupling between the granular pile dilatancy and the interstitial fluid pressure generated by the impact. Our results provide a generic mechanism for explaining the wide variety of impact responses in particulate media, from dry quicksand in powders to impact-hardening in shear-thickening suspensions like cornstarch.Impacts on particulate media like granular materials and suspensions present an astonishingly rich phenomenology [1, 2]. Along with its astrophysical [3] and ballistics applications [4], impact dynamics is an object of active research to understand the high-speed response of granular matter [5]. In dry granular media, impact by a solid object results in the formation of a corona of granular ejecta and a solid-like plastic deformation leading to a permanent crater [6][7][8][9][10][11]. For fine powders in air, granular jets and cavity collapse occur during impact [12,13]. Subsequent studies showed that the ambient pressure of the interstitial fluid (air) is an important element for the observed fluid-like behavior [14][15][16], while for denser packing the impact penetration is much reduced [17]. However, the question of the physical mechanisms and control parameters that give rise to such a wide variety of phenomena is still largely open. Recently, studies on shearthickening suspensions (cornstarch) showed completely different behaviors. Above a critical velocity, an impacting object immediately stops [18], or in some cases generates cracks [19], as if hitting a solid. This phenomenon has been related to the propagation of dynamic jamming fronts in the bulk [18] but the mechanism remains unclear and overlooks the role of fluid/grains couplings, which are known to strongly affect the transient behavior of saturated granular materials [2,20,21]. Whether impact-activated solidification relies on such couplings or on the complex rheology of the suspension is a pivotal question for clarifying the physics of shear-thickening fluids -a still highly debated topic [23][24][25][26][27].The objective of this Letter is to address these questions and elucidate the role of the interstitial fluid and the initial volume fraction on the diverse impact phenomenology observed in granular materials and dense suspensions during the last decade. To avoid difficulties associated with colloidal interactions between particles (like in shear-thickening suspensions) or fluid compressibility (like in powders in air), we study here the impact of a freely-falling rigid sphere on a simple granular suspension [28] made up of macroscopic, heavy particles (glass beads in the range 0.1-1 mm) immersed in an incompressible liquid (water, viscous oil). The initial packing fraction of the suspension φ 0 (the ratio of the volume of the glass beads to the total v...

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confidence: 99%

Unifying Impacts in Granular Matter from Quicksand to Cornstarch

2016

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“…A different explanation relies on the presence of interstitial gas throughout the bed. In situations where the gas permeability is low, i.e., fine-grained beds, the gas is effectively trapped during the short impact duration and can resist global packing density changes [15]. For loose packings this leads to a response whereby a large portion of the bed surrounding the impact behaves similar to an incompressible liquid, allowing the impactor to sink in [18].…”

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confidence: 99%

“…Probing the resulting combination of liquidand solid-like properties a number of recent studies investigated the impact of a large object into a bed of dry grains. These studies focused on issues such as the drag on the impacting object [1-6], crater formation [7-10] the corona-like splash formed immediately after the impactor hits the bed surface [10], and the subsequent jet of grains formed by the collapse of the cavity left by the impactor [11][12][13][14][15][16]. So far however, almost all work considered the limit of loosely packed, marginally stable beds that readily compact in response to perturbations.…”

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The role of interstitial gas in determining the impact response of granular beds

Royer¹,

Conyers²,

Corwin³

et al. 2011

EPL

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Abstract. -We examine the impact of a solid sphere into a fine-grained granular bed. Using high-speed X-ray radiography we track both the motion of the sphere and local changes in the bed packing fraction. Varying the initial packing density as well as the ambient gas pressure, we find a complete reversal in the effect of interstitial gas on the impact response of the bed: The dynamic coupling between gas and grains allows for easier penetration in initially loose beds but impedes penetration in more densely packed beds. High-speed imaging of the local packing density shows that these seemingly incongruous effects have a common origin in the resistance to bed packing changes caused by interstitial air.Introduction. -Granular materials often exhibit behavior intermediate between that of conventional solids and liquids. Probing the resulting combination of liquidand solid-like properties a number of recent studies investigated the impact of a large object into a bed of dry grains. These studies focused on issues such as the drag on the impacting object [1-6], crater formation [7-10] the corona-like splash formed immediately after the impactor hits the bed surface [10], and the subsequent jet of grains formed by the collapse of the cavity left by the impactor [11][12][13][14][15][16]. So far however, almost all work considered the limit of loosely packed, marginally stable beds that readily compact in response to perturbations. On the other hand, densely packed beds must dilate in order for grains to move out of the way of inserted objects. This implies different resistance not only for slow, quasi-static perturbations [17] but also suggests that there should be a significant change in the dynamics for faster impacts.An important feature of the impact dynamics in granular systems is the coupling between the interstitial gas, typically air, and the grain packing. For fine grained beds (grain diameters below ∼ 150 µm) this interaction can drastically change the impact dynamics. In particular, in

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“…The focus here was on impact of non-Newtonian fluids, but investigations of many other research topics, such as liquid drop breakup 19,20 , granular jets 21 , and liquid drop coalescence 22 , benefit from a similar technique. Such experimental approach makes it possible to image microscale phenomena and at the same time obtain insights into the accompanying dynamics at the scale of microseconds, a regime that is challenging for conventional imaging methods.…”

Section: Discussionmentioning

confidence: 99%

Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids

Peters

Wilken

et al. 2014

JoVE

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In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for detailed observation, scenarios that make it challenging to observe with conventional imaging systems. One of these is the drop impact of liquids, which usually happens within one tenth of millisecond. To tackle this challenge, a fast imaging technique is introduced that combines a high-speed camera (capable of up to one million frames per second) with a macro lens with long working distance to bring the spatial resolution of the image down to 10 µm/pixel. The imaging technique enables precise measurement of relevant fluid dynamic quantities, such as the flow field, the spreading distance and the splashing speed, from analysis of the recorded video. To demonstrate the capabilities of this visualization system, the impact dynamics when droplets of non-Newtonian fluids impinge on a flat hard surface are characterized. Two situations are considered: for oxidized liquid metal droplets we focus on the spreading behavior, and for densely packed suspensions we determine the onset of splashing. More generally, the combination of high temporal and spatial imaging resolution introduced here offers advantages for studying fast dynamics across a wide range of microscale phenomena. Video LinkThe video component of this article can be found at

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Birth and growth of a granular jet

Cited by 30 publications

References 30 publications

Unifying Impacts in Granular Matter from Quicksand to Cornstarch

Unifying Impacts in Granular Matter from Quicksand to Cornstarch

The role of interstitial gas in determining the impact response of granular beds

Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids

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