Effects of density ratio, rotation speed, and fill level on density-induced granular streak segregation in a rotating drum

Liao, Chun Chung; Hsiau, Shu San; Nien, H. C.

doi:10.1016/j.powtec.2015.07.030

Cited by 32 publications

(14 citation statements)

References 30 publications

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“…Flowing mixtures of granular material with differing properties, including size [2][3][4][5][6][7][8], density [9][10][11][12][13][14][15][16], surface roughness [17,18], and shape [19,20], tend to segregate, and they are common in geophysical flows [21][22][23][24] and industrial settings such as during hopper filling and discharging [25][26][27], in rotating tumblers [9,[28][29][30][31][32], and in chute flow [1,33,34]. The simplest explanation for segregation relies on the idea, for size-disperse mixtures, that small particles fall through voids generated between large particles and accumulate in the lower regions of the flowing layer, while large particles are forced upward by concentrated regions of small particles.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric concentration dependence of segregation fluxes in granular flows

et al. 2018

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We characterize the local concentration dependence of segregation velocity and segregation flux in both size and density bidisperse gravity-driven free-surface granular flows as a function of the particle size ratio and density ratio, respectively, using discrete element method (DEM) simulations. For a range of particle size ratios and inlet volume flow rates in size-bidisperse flows, the maximum segregation flux occurs at a small particle concentration less than 0.5, which decreases with increasing particle size ratio. The segregation flux increases up to a size ratio of 2.4 but plateaus from there to a size ratio of 3. In density bidisperse flows, the segregation flux is greatest at a heavy particle concentration less than 0.5 which decreases with increasing particle density ratio. The segregation flux increases with increasing density ratio for the extent of density ratios studied, up to 10. We further demonstrate that the simulation results for size driven segregation are in accord with the predictions of the kinetic sieving segregation model of Savage and Lun [1]. arXiv:1806.07993v1 [physics.flu-dyn]

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Section: Introductionmentioning

confidence: 99%

Asymmetric concentration dependence of segregation fluxes in granular flows

et al. 2018

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“…Among different particle properties that can drive segregation, particle size [13] and density [14] are critical factors. The focus of this work is the segregation due to differences in particle density, which can occur in vibrated granular mixtures [15][16][17][18][19], free surface flows [20][21][22][23][24] and vertical chute flows [25]. In gravity-driven free surface flows, particles with lower density are more likely to rise to the free surface while particles with higher density are more likely to segregate to the bottom of the flowing layer, resulting in segregation patterns such as a segregated core or streaks of heavier particles in rotating tumblers [14,[21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…The focus of this work is the segregation due to differences in particle density, which can occur in vibrated granular mixtures [15][16][17][18][19], free surface flows [20][21][22][23][24] and vertical chute flows [25]. In gravity-driven free surface flows, particles with lower density are more likely to rise to the free surface while particles with higher density are more likely to segregate to the bottom of the flowing layer, resulting in segregation patterns such as a segregated core or streaks of heavier particles in rotating tumblers [14,[21][22][23]. While particle-based simulation methods can reproduce density-driven segregation phenomena on a small scale, an accurate continuum-based model would be of clear practical and theoretical value.…”

Section: Introductionmentioning

confidence: 99%

Modelling density segregation in flowing bidisperse granular materials

Xiao¹,

Umbanhowar²,

Ottino³

2016

Proc. R. Soc. A.

145

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Preventing segregation in flowing granular mixtures is an ongoing challenge for industrial processes that involve the handling of bulk solids. A recent continuum-based modelling approach accurately predicts spatial concentration fields in a variety of flow geometries for mixtures varying in particle size. This approach captures the interplay between advection, diffusion and segregation using kinematic information obtained from experiments and/or discrete element method (DEM) simulations combined with an empirically determined relation for the segregation velocity. Here, we extend the model to include density-driven segregation, thereby validating the approach for the two important cases of practical interest. DEM simulations of density bidisperse flows of mono-sized particles in a quasi-two-dimensional-bounded heap were performed to determine the dependence of the density-driven segregation velocity on local shear rate and particle concentration. The model yields theoretical predictions of segregation patterns that quantitatively match the DEM simulations over a range of density ratios and flow rates. Matching experiments reproduce the segregation patterns and quantitative segregation profiles obtained in both the simulations and the model, thereby demonstrating that the modelling approach captures the essential physics of density-driven segregation in granular heap flow.

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“…Stratification via flow modulation occurs in tridisperse size mixtures and should also occur for mixtures of particles differing in material density, because density segregation in bounded heaps shares many similarities with size segregation [51] and layering of density bidisperse materials has been observed in rotating tumbler flow [62]. Further work is necessary to better explore these topics.…”

Section: Discussionmentioning

confidence: 99%

Controlling granular segregation using modulated flow

et al. 2017

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Unsteady flows of granular media are ubiquitous yet remain largely unexplored. In this research, we apply unsteady flows to strongly segregating granular materials to control the segregation pattern and enhance overall mixing. Sizebidisperse granular mixtures with large size ratios flowing onto a quasi-2D bounded heap form stratified layers of large and small particles when the flow rate is modulated. These layers exhibit better average mixing than the segregated patterns generated by steady feed rates. The mechanisms of layer formation under modulated flow differ from those for spontaneous stratification and are related to changes in the composition of the flowing layer at different stages in each feed cycle. The thickness and length of the stratified layers can be controlled by changing the feed rates and feed cycle durations, which is potentially useful for reducing segregation in industrial processes.

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Effects of density ratio, rotation speed, and fill level on density-induced granular streak segregation in a rotating drum

Cited by 32 publications

References 30 publications

Asymmetric concentration dependence of segregation fluxes in granular flows

Asymmetric concentration dependence of segregation fluxes in granular flows

Modelling density segregation in flowing bidisperse granular materials

Controlling granular segregation using modulated flow

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