Stokes' cradle: normal three-body collisions between wetted particles

Donahue, Carly M.; Hrenya, Christine M.; Davis, Robert H.; Nakagawa, K. J.; Zelinskaya, A. P.; Joseph, G. G.

doi:10.1017/s0022112009993715

Cited by 42 publications

(70 citation statements)

References 16 publications

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“…Surprisingly, the trends are different depending on whether de-agglomeration occurs for values of St n less than St * n or greater than St * n , the value of the Stokes number at which normal (head-on) collisions transition from stick to 146 C. M. Donahue, W. M. Brewer, R. H. Davis and C. M. Hrenya For St n < St * n For St n > St * n Figure As e dry ↑, e w,n ↔ (Experiment) ↑ (Experiment) 8 ↔ (Theory) ↑ (Theory) As e dry ↑, θ R ↔ (Experiment) ↔ (Experiment) 8 ↔ (Theory) ↔ (Theory) As µ ↑, e w,n ↔ (Experiment) ↑ (Experiment) 9 ↔ (Theory) ↑ (Theory) As µ ↑, θ R ↔ (Experiment) ↓ (Experiment) 9 ↔ (Theory) ↓ (Theory) As x 0 ↑, e w,n ↔ (Experiment) ↓ (Experiment) 10 ↔ (Theory) ↓ (Theory) As x 0 ↑, θ R ↔ (Experiment) ↑ (Experiment) 10 ↔ (Theory) ↑ (Theory) As a ↑, e w,n ↓ (Experiment) ↔ (Experiment) 11 ↓ (Theory) ↔ (Theory) As a ↑, θ R ↓ (Experiment) ↔ (Experiment) 11 ↓ (Theory) ↔ (Theory) bounce. Since the collision dynamics and de-agglomeration are primarily influenced by the particle deformation and reversal criteria associated with normal collisions when St n > St * n , the same trends are observed here as in previous normal particle-particle collisions (Donahue et al 2010b). However, centrifugal forces, which dominate the de-agglomeration process for St n < St * n , do not have the same dependence on the experimental parameters; accordingly, the values of e w,n and θ R are not very sensitive to any of the parameters varied for both experiment and theory predictions (within experimental error).…”

Section: Discussionsupporting

confidence: 86%

“…In previous work, the glass-transition rebound criterion dictated the reversal process for the conditions investigated and was critical in the prediction of the correct outcomes and trends for normal three-body collisions (Donahue et al 2010b). In that three-body work, a pendulum apparatus was also used, and the materials and the range of parameters used were similar to this work.…”

Section: Reversal Criteriamentioning

confidence: 92%

“…First, the pressure in the liquid gap rapidly increases during approach; if the pressure exceeds the glasstransition pressure, p gt , then the liquid behaves as a solid and the particles reverse direction. The glass-transition rebound separation is (Donahue et al 2010b). The glass transition can be viewed as a limiting case of non-Newtonian behaviour, wherein the effective viscosity of the liquid film becomes very large at very high compressive pressures (Barnocky & Davis 1989).…”

Section: Reversal Criteriamentioning

confidence: 99%

“…In that three-body work, a pendulum apparatus was also used, and the materials and the range of parameters used were similar to this work. The theory used in Donahue et al (2010b) is the same as in this work for head-on collisions with ω = ξ = 0. Therefore, not surprisingly, the glass-transition state is the first reversal criterion met in the theoretical predictions here.…”

Section: Reversal Criteriamentioning

confidence: 99%

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Agglomeration and de-agglomeration of rotating wet doublets

et al. 2012

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In this work, experiments using a pendulum apparatus were conducted for two particles engaged in oblique, wetted collisions over a range of impact angles, impact velocities, coating thicknesses, liquid viscosities, particle materials, and particle radii. From previous studies on normal or head-on collisions, the two particles bounce apart if the Stokes number (a ratio of particle inertia to viscous forces) exceeds a critical value, whereas they stick together if the Stokes number is below this critical value. However, for oblique collisions, an additional outcome is observed at moderate Stokes numbers and impact angles, in which the spheres initially stick together, rotate as a doublet, and then separate due to centrifugal forces. We refer to this outcome as 'stick-rotate-separate'. For subcritical Stokes numbers exhibiting this new outcome, the experimental results for the apparent coefficient of normal restitution and angle of rotation from impact to separation show only weak dependence on the fluid viscosity and thickness and the dry restitution coefficient, whereas they both decrease with increasing particle radius. These results are in contrast with those for supercritical Stokes numbers in which the spheres bounce upon impact. An accompanying theory based on lubrication forces, the glass transition of the liquid layer, and solid deformation and rebound agrees well with experimental results and gives insight into the observed trends.

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Section: Discussionsupporting

confidence: 86%

Section: Reversal Criteriamentioning

confidence: 92%

Section: Reversal Criteriamentioning

confidence: 99%

Section: Reversal Criteriamentioning

confidence: 99%

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Agglomeration and de-agglomeration of rotating wet doublets

et al. 2012

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“…Recent developments of the original elastohydrodynamic rebound problem 11 by Donahue et al 16,17 assume a constant (Newtonian) viscosity all the way down to a cut-off lengthscale, x gt , at which point the pressure in the fluid (O(10 8 ) Pa) induces a "glass transition." This approach appears to neglect the shear-thinning effects in the oil films which coat the solids in the above-mentioned studies.…”

Section: Introductionmentioning

confidence: 99%

Squeeze flow of a Carreau fluid during sphere impact

2012

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Articles you may be interested inWe present results from a combined numerical and experimental investigation into the squeeze flow induced when a solid sphere impacts onto a thin, ultra-viscous film of non-Newtonian fluid. We examine both the sphere motion through the liquid as well as the fluid flow field in the region directly beneath the sphere during approach to a solid plate. In the experiments we use silicone oil as the model fluid, which is welldescribed by the Carreau model. We use high-speed imaging and particle tracking to achieve flow visualisation within the film itself and derive the corresponding velocity fields. We show that the radial velocity either diverges as the gap between the sphere and the wall diminishes (Z tip → 0) or that it reaches a maximum value and then decays rapidly to zero as the sphere comes to rest at a non-zero distance (Z tip = Z min ) away from the wall. The horizontal shear rate is calculated and is responsible for significant viscosity reduction during the approach of the sphere. Our model of this flow, based on lubrication theory, is solved numerically and compared to experimental trials. We show that our model is able to correctly describe the physical features of the flow observed in the experiments. C 2012 American Institute of Physics. [http://dx

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Granulation of snow: From tumbler experiments to discrete element simulations

Steinkogler

Gaume²,

Löwe³

et al. 2015

J. Geophys. Res. Earth Surf.

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It is well known that snow avalanches exhibit granulation phenomena, i.e., the formation of large and apparently stable snow granules during the flow. The size distribution of the granules has an influence on flow behavior which, in turn, affects runout distances and avalanche velocities. The underlying mechanisms of granule formation are notoriously difficult to investigate within large-scale field experiments, due to limitations in the scope for measuring temperatures, velocities, and size distributions. To address this issue we present experiments with a concrete tumbler, which provide an appropriate means to investigate granule formation of snow. In a set of experiments at constant rotation velocity with varying temperatures and water content, we demonstrate that temperature has a major impact on the formation of granules. The experiments showed that granules only formed when the snow temperature exceeded −1 ∘ C. No evolution in the granule size was observed at colder temperatures. Depending on the conditions, different granulation regimes are obtained, which are qualitatively classified according to their persistence and size distribution. The potential of granulation of snow in a tumbler is further demonstrated by showing that generic features of the experiments can be reproduced by cohesive discrete element simulations. The proposed discrete element model mimics the competition between cohesive forces, which promote aggregation, and impact forces, which induce fragmentation, and supports the interpretation of the granule regime classification obtained from the tumbler experiments. Generalizations, implications for flow dynamics, and experimental and model limitations as well as suggestions for future work are discussed.

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Stokes' cradle: normal three-body collisions between wetted particles

Cited by 42 publications

References 16 publications

Agglomeration and de-agglomeration of rotating wet doublets

Agglomeration and de-agglomeration of rotating wet doublets

Squeeze flow of a Carreau fluid during sphere impact

Granulation of snow: From tumbler experiments to discrete element simulations

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