Predicting segregation of nonspherical particles

Jones, Ryan P.; Ottino, Julio M.; Umbanhowar, Paul B.; Lueptow, Richard M.

doi:10.1103/physrevfluids.6.054301

Cited by 10 publications

(21 citation statements)

References 61 publications

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“…The validity of an instantaneous segregation assumption can be evaluated relative to two dimensionless parameters, the ratio of the advection timescale to the segregation timescale, Ω = SL / h 2 , and the Péclet number, which is the ratio of the advection timescale to the diffusion timescale, Pe = 2 qh / DL (Fan et al., 2014). We explore these parameters using a range of values for the length scale, 0.1 ≤ L ≤ 20 m, which represents the length of a mesh cell to ≈1/4 the flume length; the flowing layer depth, 0.2 ≤ h ≤ 0.5 m, which are the range of depths observed in channel flow; the segregation length scale 5 × 10 −5 ≤ S ≤ 2 × 10 −4 m (Jones et al., 2020, 2021; Schlick et al., 2015) for a reference particle diameter, d , of 0.25–1 mm; a 2D flow rate, 1 ≤ q = hv ≤ 5 m 2 /s; and a diffusion coefficient, 1.25 × 10 −6 ≤ D ∝ ( v / h ) d 2 ≤ 2.5 × 10 −5 m 2 /s (Fan et al., 2014). The non‐dimensional numbers then range as 2 × 10 −5 ≤ Ω ≤ 0.1 and 800 ≤ Pe ≤ 4 × 10 7 .…”

Section: Methodsmentioning

confidence: 99%

“…Importantly, the materials of two different species can have overlapping distributions of material properties, including those that lead to a segregated state (Gao et al, 2021). The rate of segregation is non-linear with concentration (Gajjar & Gray, 2014;Jones et al, 2018) and depends on the magnitude of the difference between the material properties (Jones et al, 2020(Jones et al, , 2021Schlick et al, 2015).…”

Section: Segregation Sub-modelmentioning

confidence: 99%

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Simulating Debris Flow and Levee Formation in the 2D Shallow Flow Model D‐Claw: Channelized and Unconfined Flow

Jones

Rengers

Barnhart

et al. 2023

Earth and Space Science

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Debris flow runout poses a hazard to life and infrastructure. The expansion of human population into mountainous areas and onto alluvial fans increases the need to predict and mitigate debris flow runout hazards. Debris flows on unconfined alluvial fans can exhibit spontaneous self‐channelization through levee formation that reduces lateral spreading and extends runout distances compared to unchannelized flows. Here we modify the D‐Claw shallow flow model in two ways that are hypothesized to generate levees. We evaluate these modifications with observations from a large‐scale flume experiment. We investigate model performance when including the effect of two different friction sub‐models, as well as the inclusion of segregation effects on granular permeability. Results show that, for a wide range of plausible model input parameters, simulations including the effects of segregation promoted modeled levee formation, whereas simulations without the effects of segregation did not create levees. Further, using a forward predictive framework, simulations with the effects of segregation were more likely to better model the magnitude of debris flow depth and runout distance, whereas simulation timing of the debris flow was affected by the choice of friction sub‐model. Our results indicate that including the effects of segregation on granular permeability can improve the likelihood of better predictions of debris flow depth and runout prior to an event occurring.

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Section: Methodsmentioning

confidence: 99%

Section: Segregation Sub-modelmentioning

confidence: 99%

Simulating Debris Flow and Levee Formation in the 2D Shallow Flow Model D‐Claw: Channelized and Unconfined Flow

Jones

Rengers

Barnhart

et al. 2023

Earth and Space Science

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“…The advantage of this approach is that the sizes and densities of the two particle species need not be known in advance, and, more significantly, no analog to Figure 3 is necessary (which requires many experiments or simulations). This makes the approach applicable for particles that may vary in properties other than just size or density, such as shape 16 . Using this approach, a few simple experiments can determine the equilibrium concentration that minimizes segregation.…”

Section: Methods To Determine Equilibrium Concentrationmentioning

confidence: 99%

Designing minimally segregating granular mixtures for gravity‐driven surface flows

et al. 2023

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In dense flowing bidisperse particle mixtures varying in size or density alone, smaller particles sink (percolation-driven) and lighter particles rise (buoyancy-driven). But when particle species differ from each other in both size and density, percolation and buoyancy can either enhance (large/light and small/heavy) or oppose (large/heavy and small/light) each other. In the latter case, a local equilibrium can exist in which the two mechanisms balance and particles remain mixed: this allows the design of minimally segregating mixtures by specifying particle size ratio, density ratio, and mixture concentration. Using DEM simulations, we show that mixtures specified by the design methodology remain relatively well-mixed in heap and tumbler flows. Furthermore, minimally segregating mixtures prepared in a fully segregated state in a tumbler mix over time and eventually reach a nearly uniform concentration. Tumbler experiments with large steel and small glass particles validate the DEM simulations and the potential for designing minimally segregating mixtures.

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“…Owing to the intrinsic dissipation, external energy has to be continuously injected into granular system to keep grains in motion. Various segregation agitation methods, i.e., shear and vibration, have been used to separate and mix binary grains [13][14][15][16][17]. Many driving mechanism based on materials properties, i.e., percolation and buoyancy, have also been proposed to describe the segregation of binary mixtures [18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Resonance-induced acceleration of the RBNE-BNE segregation inversion of granular mixtures

Shao¹,

Li²,

Wang³

et al. 2022

Preprint

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This paper presents the experiments and simulations on the resonance-induced acceleration of the reverse Brazil nut effect (RBNE)-Brazil nut effect (BNE) segregation inversion of binary mixtures in flat-bottom and circular-bottom containers. Both experimental and simulation results indicate that the starting location of the sinkage of heavier grains at the top layer is triggered with certain randomness in the flat-bottom container, whereas it first occurs at either of the lateral edges of the bottom in the circular-bottom container. The quantified segregation factors in simulations show that the transition from the RBNE segregation state to the BNE segregation state happens faster in the circular-bottom container than that in the flat-bottom container. The occurrence of standing-wave resonant spots of higher and lower granular temperature accelerates the RBNE-BNE segregation inversion. From the elastic collision model of single grain, the bottom with a larger angle leads to more energy transfer from the vertical direction to the horizontal direction. The theoretical predictions are confirmed by the simulations of a monodisperse granular bed. The flatbottom container has a uniform distribution with a standing-wave period of granular temperature and packing density, whereas the circular-bottom container possesses a higher granular temperature in the horizontal direction and a lower packing density at the lateral edges of the circular bottom. Owing to the buoyancy effect, heavier grains easily sink first at the resonant spots with higher temperature.

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Predicting segregation of nonspherical particles

Cited by 10 publications

References 61 publications

Simulating Debris Flow and Levee Formation in the 2D Shallow Flow Model D‐Claw: Channelized and Unconfined Flow

Simulating Debris Flow and Levee Formation in the 2D Shallow Flow Model D‐Claw: Channelized and Unconfined Flow

Designing minimally segregating granular mixtures for gravity‐driven surface flows

Resonance-induced acceleration of the RBNE-BNE segregation inversion of granular mixtures

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