Experimental measurements of the collapse of a two-dimensional granular gas under gravity

Son, Reuben; Pérez, John; Voth, Greg

doi:10.1103/physreve.78.041302

Cited by 12 publications

(61 citation statements)

References 17 publications

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“…Comparison of different decay laws for the case of decay with no production and initial condition R(t = 0) = 1 kJ/m 3 . Buser and suggest an exponential decay that agrees with the granular collapse experiments in gravity by Son et al [2008], who fitted decay times with power coefficients varying between n = 3 and n = 6, R / f (t n ). The collisional law of Haff [1983] is only valid for collisional systems without enduring particle contacts.…”

Section: Energy Fluxessupporting

confidence: 82%

“…The fraction βR must be subtracted from the production of R . Thus,

\dot{italicE} = (1 - α) {\overset{W}{true}}_{italicf} + β R and \dot{italicR} = α {\overset{W}{true}}_{italicf} - β R .

This decay − βR with constant fraction β has been identified in granular collapse experiments under gravity by Son et al [2008], who fitted the experimental collapse measurements of the decay of R in time with power laws. As can be seen in Figure 13, a power law time decay can be as well approximated by an exponential decay,

\overset{R}{true}

= − βR .…”

Section: Model Equationsmentioning

confidence: 64%

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Modeling mass‐dependent flow regime transitions to predict the stopping and depositional behavior of snow avalanches

Bartelt¹,

Bühler²,

Buser³

et al. 2012

J. Geophys. Res.

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.[1] How terrain, snow cover properties, and release conditions combine to determine avalanche speed and runout remains the central problem in avalanche science. Here we report on efforts to understand how surface roughness, snow properties, and internal mass fluxes control the generation of granular fluctuation energy within the basal shear layers of dense flowing snow avalanches, and the subsequent influence on avalanche speed and deposition patterns. For this purpose we augment the depth-averaged equations of motion to account for the generation of the kinetic energy associated with the particle fluctuations, and dissipation of this energy by collisional and frictional material interactions. Using high-resolution laser scans of the preevent snow cover and postevent deposits from two avalanches released at the Swiss Vallée de la Sionne observation station, we compare measured and calculated deposition heights. The model captures flow velocities and deposition heights without ad hoc adjustments of the constitutive parameters according to avalanche size. The model parameters are separated into a terrain and other pure material (snow) parameters. The investigations reveal how release conditions and snow entrainment influence the internal mass distribution, and control flow regime transitions between the fluidized regime (head) and plug regime (tail). The comparison between the measured and calculated velocities and deposition heights demonstrates why standard Voellmy-type submodels are suitable for many practical mitigation problems, but also why they are limited to cases where the calibrated parameters, already accounting for terrain, snow cover properties, avalanche size, and mass intake, are known.

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Section: Energy Fluxessupporting

confidence: 82%

“…The fraction βR must be subtracted from the production of R . Thus,

\dot{italicE} = (1 - α) {\overset{W}{true}}_{italicf} + β R and \dot{italicR} = α {\overset{W}{true}}_{italicf} - β R .

\overset{R}{true}

= − βR .…”

Section: Model Equationsmentioning

confidence: 64%

Modeling mass‐dependent flow regime transitions to predict the stopping and depositional behavior of snow avalanches

Bartelt¹,

Bühler²,

Buser³

et al. 2012

J. Geophys. Res.

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“…In addition, it is possible to identify a novel regime of cooling quantitatively for low rates of compaction. This is only possible in microgravity as under the dominating influence of gravity granular gases collapse quite rapidly [13]. The newly identified cooling extends over several seconds and is described reasonably well by a linear decay of ∆(t).…”

Section: Resultsmentioning

confidence: 97%

“…On ground the compaction is dominated by gravity-induced sedimentation and takes place rather rapidly within a fraction of a second and also comparably violently with shock waves traveling through the system [13]. In microgravity, the energy loss is still driven by interparticle collision but the rapid sedimentation is replaced by the compaction from the container walls which is chosen here to be rather moderate in speed.…”

Section: X-ray Radiographymentioning

confidence: 99%

Monitoring three-dimensional packings in microgravity

Frank-Richter

Börngen

et al. 2014

Granular Matter

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We present results from experiments with granular packings in three dimensions in microgravity as realized on parabolic flights. Two different techniques are employed to monitor the inside of the packings during compaction: (1) X-ray radiography is used to measure in transmission the integrated fluctuations of particle positions. (2) Stress-birefringence in three dimensions is applied to visualize the stresses inside the packing. The particle motions below the transition into an arrested packing are found to produce a well agitated state. At the transition, the particles lose their energy quite rapidly and form a stress network. With both methods, non-arrested particles (rattlers) can be identified. In particular, it is found that rattlers inside the arrested packing can be excited to appreciable dynamics by the restaccelerations (g-jitter) during a parabolic flight without destroying the packings. At low rates of compaction, a regime of slow granular cooling is identified. The slow cooling extends over several seconds, is described well by a linear law, and terminates in a rapid final collapse of dynamics before complete arrest of the packing.

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“…discussed in Refs. [53][54][55][56][57]. In addition in the next section we will show that also for the more complex process when gravity acts during deposition (sec.…”

Section: Collapse After Deposition Completementioning

confidence: 99%

Density profiles of loose and collapsed cohesive granular structures generated by ballistic deposition

Kadau

Herrmann

2011

Phys. Rev. E

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Loose granular structures stabilized against gravity by an effective cohesive force are investigated on a microscopic basis using contact dynamics. We study the influence of the granular Bond number on the density profiles and the generation process of packings, generated by ballistic deposition under gravity. The internal compaction occurs discontinuously in small avalanches and we study their size distribution. We also develop a model explaining the final density profiles based on insight about the collapse of a packing under changes of the Bond number.

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Experimental measurements of the collapse of a two-dimensional granular gas under gravity

Cited by 12 publications

References 17 publications

Modeling mass‐dependent flow regime transitions to predict the stopping and depositional behavior of snow avalanches

Modeling mass‐dependent flow regime transitions to predict the stopping and depositional behavior of snow avalanches

Monitoring three-dimensional packings in microgravity

Density profiles of loose and collapsed cohesive granular structures generated by ballistic deposition

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