Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session F20: Granular Flows IIGranular
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Chair: Nathalie Vriend, University of Cambridge Room: 704 |
Monday, November 20, 2017 8:00AM - 8:13AM |
F20.00001: Why do lab-scale experiments ever resemble geological scale patterning? Behrooz Ferdowsi, Brandon C. Jones, Jeremy L. Stein, Troy Shinbrot The Earth and other planets are abundant with curious and poorly understood surface patterns. Examples include sand dunes, periodic and aperiodic ridges and valleys, and networks of river and submarine channels. We make the minimalist proposition that the dominant mechanism governing these varied patterns is mass conservation: notwithstanding detailed particulars, the universal rule is mass conservation and there are only a finite number of surface patterns that can result from this process. To test this minimalist proposition, we perform experiments in a vertically vibrated bed of fine grains, and we show that every one of a wide variety of patterns seen in the laboratory is also seen in recorded geomorphologies. We explore a range of experimental driving frequencies and amplitudes, and we complement these experimental results with a non-local cellular automata model that reproduces the surface patterns seen using a minimalist approach that allows a free surface to deform subject to mass conservation and simple known forces such as gravity. These results suggest a common cause for the effectiveness of lab-scale models for geological scale patterning that otherwise ought to have no reasonable correspondence. [Preview Abstract] |
Monday, November 20, 2017 8:13AM - 8:26AM |
F20.00002: Accretion Dynamics on Wet Granular Materials Guillaume Saingier, Alban Sauret, Pierre Jop Blending liquid with dry grains constitutes the initial step of industrial processes such as granulation. As the first grains become wet, they aggregate. More dry grains can then stick to the aggregates, eventually producing a uniformly wet granular material. The mechanism responsible of the capture of dry grains and the growth of the aggregates involve interfacial effects and granular dynamics. To describe the interplay between the grains and the liquid, we carry out a model experiment, in which the pressure of the liquid in the wet saturated aggregate is controlled. We highlight the existence of two different growth regimes, whose dynamics are limited by fluid present at the surface of the aggregate and the number of particles impacting. The transition between the two regimes is governed by the liquid availability at the interface, as it appears to directly control the probability of grain capture. [Preview Abstract] |
Monday, November 20, 2017 8:26AM - 8:39AM |
F20.00003: Interfacial Granular Intrusions Paul Linden, Zhong Zheng, Herbert Huppert, Nathalie Vriend, Jerome Neufeld We study experimentally the intrusion of light granular material into an inviscid fluid of greater density. Despite a rich set of related geophysical and environmental phenomena, such as the spreading of calved ice and volcanic ash and debris flows, there are few previous studies on this topic. We conduct a series of lock-release experiments of light spherical beads into a rectangular tank initially filled with either fresh water or salt water, and record the time evolution of the interface shape and the front location of the current of beads. In particular, we find that the front location obeys a power-law behaviour during an intermediate time period following the release of the lock before the nose of beads reaches a maximum runout distance within a finite time. We investigate the dependence of the scaling exponent and runout distance on the total amount of beads, the initial lock length, and the properties of the liquid that fills the tank in the experiments. Appropriate scaling arguments are provided to collapse the raw experimental data into universal curves, which can be used to describe the front dynamics of light granular intrusions with different size and buoyancy effects and initial aspect ratios. [Preview Abstract] |
Monday, November 20, 2017 8:39AM - 8:52AM |
F20.00004: Study of an athermal quasi static plastic deformation in a 2D granular material Jie Zhang In crystalline materials, the plasticity has been well understood in terms of dynamics of dislocation, i.e. flow defects in the crystals where the flow defects can be directly visualized under a microscope. In a contrast, the plasticity in amorphous materials, i.e. glass, is still poorly understood due to the disordered nature of the materials. In this talk, I will discuss the recent results we have obtained in our ongoing research of the plasticity of a 2D glass in the athermal quasi static limit where the 2D glass is made of bi-disperse granular disks with very low friction. Starting from a densely packed homogeneous and isotropic initial state, we apply pure shear deformation to the system. For a sufficiently small strain, the response of the system is linear and elastic like; when the strain is large enough, the plasticity of the system gradually develops and eventually the shear bands are fully developed. In this study, we are particularly interested in how to relate the local plastic deformation to the macroscopic response of the system and also in the development of the shear bands. [Preview Abstract] |
Monday, November 20, 2017 8:52AM - 9:05AM |
F20.00005: Impact cratering in sand: Comparing solid and liquid intruders Devaraj van der Meer, Rianne de Jong, Song-Chuan Zhao How does the impact of a deformable droplet on a granular bed differ from that caused by a solid impactor of similar size and density? Here, we experimentally study this question and focus on the effect of intruder deformability on the crater shape. We will show that, for comparable impact speeds, the crater diameter is larger for droplets than for solid intruders, but that the latter result in deeper craters. Interestingly, for initially dense beds of packing fractions larger than 0.58, we find that the resultant excavated crater volume is independent of the intruder deformability, indicating an impactor-independent dissipation mechanism within the sand for these dense beds. [Preview Abstract] |
Monday, November 20, 2017 9:05AM - 9:18AM |
F20.00006: Not quite liquid rope coiling James Hanna, Nicholas Corbin, Wesley Royston, Harmeet Singh, Rick Warner The coiling of liquid and solid ropes onto surfaces has been the complicated subject of several recent studies. Here we discuss the related problem of impact of a discrete ball-and-link chain, an object whose dynamics often mimic those of a continuous one-dimensional fluid or solid. Our interest is in a particular counterintuitive effect, namely that impact onto a surface induces an additional acceleration, such that a chain falling onto a table will descend faster than a chain in free fall. We employ high-speed imaging and particle tracking to examine this process in detail. We resolve an open question, confirming the existence of the effect in a typical ball-and-link chain, and note several other curious effects. In contrast with existing theoretical models of the process for a continuous string or rope, the extra acceleration begins at a finite time (or rather, distance along the chain) after impact onto a flat, non-tilted surface. The extra distance traveled by the impacting chain exhibits a complicated non-monotonic dependence on the tilt orientation of the impact surface. We speculate as to the origins of the effect, and eliminate some possible explanations. [Preview Abstract] |
Monday, November 20, 2017 9:18AM - 9:31AM |
F20.00007: Scaling law on formation and rupture of a dynamical liquid bridge Huang Zhang, Zehao Zhang, Qianfeng Liu, Shuiqing Li The formation and breakup of a pendular liquid bridge in dynamic state is investigated experimentally. The experimental setup arises from a system to measure the coefficient of restitution (COR) of a glass sphere impacting and bouncing on a wetted surface. We compare the effect of surface tension and gravity on the liquid bridge rupture by the capillary length $\kappa ^{\mathrm{-1}}$. For water and liquid 1 (50{\%} water mixed with 50{\%} glycerol), the gravity is dominant on the liquid bridge breakup. And we find that the rupture distance is in good linear trend with the non-dimensional number $G$ by the scaling law analysis. Further, for liquid 2 (25{\%} water mixed with 75{\%} glycerol) that is relatively high viscous, the linear changing of the rupture distance with the capillary number Ca is found. The relation of the rupture distance with $G$ and Ca would be helpful in understanding the complex behavior of the dynamical liquid bridge. [Preview Abstract] |
Monday, November 20, 2017 9:31AM - 9:44AM |
F20.00008: Experiments on limit-cycle memory in a soft jammed solid Nathan Keim, Jacob Hass, Devin Wieker We consider how a soft 2D jammed material forms memories of past deformations. Our experiments cyclically shear a material made of repulsive particles at an oil-water interface, observing the motion of many particles. After many shear cycles, the system approaches a steady state in which the particle trajectories form closed loops. We show how to determine whether the system was prepared with two strain amplitudes, even if the larger amplitude was applied most recently. Our results suggest a way to understand memory formation in terms of reversible and irreversible rearrangements. [Preview Abstract] |
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