Brownian Granular Flows Down Heaps

Bérut, Antoine; Pouliquen, Olivier; Forterre, Yoël

doi:10.1103/physrevlett.123.248005

Cited by 12 publications

(15 citation statements)

References 36 publications

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“…By probing a seemingly static sandpile with speckle imaging, our experiments have revealed a seething and ceaseless creeping motion-even in the near absence of mechanical disturbances. These motions are strikingly similar to recent observations of creep in a heap of Brownian (micron-scale) particles 49 , even though our sand grains are non-Brownian. Further, we have shown how granular creep rates can be tuned by imposing external disturbances that are geophysically relevant.…”

Section: Discussion and Outlooksupporting

confidence: 89%

The perpetual fragility of creeping hillslopes

et al. 2021

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Soil creeps imperceptibly but relentlessly downhill, shaping landscapes and the human and ecological communities that live within them. What causes this granular material to ‘flow’ at angles well below repose? The unchallenged dogma is churning of soil by (bio)physical disturbances. Here we experimentally render slow creep dynamics down to micron scale, in a laboratory hillslope where disturbances can be tuned. Surprisingly, we find that even an undisturbed sandpile creeps indefinitely, with rates and styles comparable to natural hillslopes. Creep progressively slows as the initially fragile pile relaxes into a lower energy state. This slowing can be enhanced or reversed with different imposed disturbances. Our observations suggest a new model for soil as a creeping glass, wherein environmental disturbances maintain soil in a perpetually fragile state.

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Section: Discussion and Outlooksupporting

confidence: 89%

The perpetual fragility of creeping hillslopes

et al. 2021

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“…Taken together, Eqs. (14) and (21) thereby provide a theoretically motivated expression ' ðnÞ model 'ðtðn;ΔÞ;ΔÞ based on properties of fragmentation kinetics and a simple mechanism for re-fragmentation formulated as a random walk. Figure 7 compares the agreement of the empirical relations δℓ empir.…”

Section: Resultsmentioning

confidence: 99%

“…Rather, the added crease length is determined only by the current total crease length and the new compaction depth. While processes that evolve logarithmically in time are readily observed in a variety of disordered physical systems, including stress or strain relaxation of a compacted sheet [17][18][19] , conductance relaxation of disordered electronic systems 20 , and creep dynamics of granular suspensions 21 , the emergence of a logarithmic model in the specific context of damage evolution in crumpled sheets is clearly distinct, and has had limited physical justification thus far.…”

mentioning

confidence: 99%

A model for the fragmentation kinetics of crumpled thin sheets

et al. 2021

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As a confined thin sheet crumples, it spontaneously segments into flat facets delimited by a network of ridges. Despite the apparent disorder of this process, statistical properties of crumpled sheets exhibit striking reproducibility. Experiments have shown that the total crease length accrues logarithmically when repeatedly compacting and unfolding a sheet of paper. Here, we offer insight to this unexpected result by exploring the correspondence between crumpling and fragmentation processes. We identify a physical model for the evolution of facet area and ridge length distributions of crumpled sheets, and propose a mechanism for re-fragmentation driven by geometric frustration. This mechanism establishes a feedback loop in which the facet size distribution informs the subsequent rate of fragmentation under repeated confinement, thereby producing a new size distribution. We then demonstrate the capacity of this model to reproduce the characteristic logarithmic scaling of total crease length, thereby supplying a missing physical basis for the observed phenomenon.

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“…For colloidal suspensions, where the diffusing particle is much bigger than the molecules or atoms comprising the surrounding fluid, a gravitational Péclet number Pe g,c is used to characterize the movement of the particles Bérut et al (2019), Russel et al (1989). It is defined by the ratio of the particle weight and the Brownian thermal forces: with d the diameter of the particles, m its buoyant mass, g the gravitational acceleration, T the temperature of the system and k B the Boltzmann constant.…”

Section: Gravitational Péclet Numbermentioning

confidence: 99%

Influence of Gravity on Atomic Mobility in a Liquid

Sondermann

Voigtmann

Meyer

2022

Microgravity Sci. Technol.

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Measurements of diffusion and thermodiffusion in liquids are very sensitive to convection caused for example by buoyancy. To reduce the impact of buoyancy-driven convection, benchmark experiments are performed in microgravity conditions. Here, we discuss the general influence of gravity on atomic mobility. The gravitational Péclet number and the gravitational length can be used to assess this influence. They show that the diffusion processes of atoms in a liquid is not affected by Earth’s gravitational force but that the process is dominated by the thermal energy of the atoms. Data from experiments under different gravity conditions ranging from $$10^{-5}g$$ 10 - 5 g to $$10^6g$$ 10 6 g are summarized. They confirm that interdiffusion is only influenced by accelerations that are orders of magnitude larger than Earth’s gravity.

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Brownian Granular Flows Down Heaps

Cited by 12 publications

References 36 publications

The perpetual fragility of creeping hillslopes

The perpetual fragility of creeping hillslopes

A model for the fragmentation kinetics of crumpled thin sheets

Influence of Gravity on Atomic Mobility in a Liquid

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