Comparing and contrasting size-based particle segregation models

Tunuguntla, Deepak R.; Weinhart, Thomas; Thornton, Anthony Richard

doi:10.1007/s40571-016-0136-1

Cited by 51 publications

(60 citation statements)

References 49 publications

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“…Some segregation theory has been extended to large size ratios (up to 10) [20] and predicts a monotonic decrease in the segregation time with the size ratio and without any change in the segregation pattern. Most of the models do not explicitly depend on the size ratio, but rather on a segregating velocity determined for each species [23]. In the few models where the size ratio is explicitly mentioned [15,20], the segregating velocity cannot change sign when the size ratio is increased, for any particle fraction.…”

Section: Introductionmentioning

confidence: 99%

Evidence of reverse and intermediate size segregation in dry granular flows down a rough incline

Thomas

d'Ortona

2018

Phys. Rev. E

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In a dry granular flow, size segregation had been shown to behave differently for a mixture containing a few large particles with a size ratio above 5 [N. Thomas, Phys. Rev. E 62, 961 (2000)1063-651X10.1103/PhysRevE.62.961]. For moderately large size ratios, large particles migrate to an intermediate depth in the bed: this is called "intermediate segregation." For the largest size ratios, large particles migrate down to the bottom of the flow: this is called "reverse segregation," in contrast with surface segregation. As the reversal and intermediate depth values depend on the fraction of particles, this numerical study mainly uses one single large tracer. Small fractions of large beads are also computed showing the link between single tracer behavior and collective segregation process. For each device (half-filled rotating tumbler and rough plane), two (2D) and three (3D) dimensional cases are distinguished. In the tumbler, the trajectories of a large tracer show that it reaches a constant depth during the flowing phase. For large size ratios, this depth is intermediate. A progressive sinking of the depth is obtained when the size ratio is increased. The largest size ratios correspond to tracers being at the bottom of the flowing layer. All 3D simulation results are in quantitative agreement with the experimental surface, intermediate, and reverse-segregation results. In the flow down a rough incline, a large tracer reaches an equilibrium depth during flow. For large size ratios, the depth is inside the bed, at an intermediate position, and for the largest size ratios, this depth is reverse, located near the bottom. Results are slightly different for a thin or a thick flow. For 3D thick flows, the reversal between surface and bottom positions occurs within a short range of size ratios: no tracer stabilizes near half-height and two reachable intermediate depth layers exist, below the surface and above the bottom reverse layer. For 3D thin flows, all intermediate depths are reachable by a tracer, depending on the size ratio. The numerical study of larger fractions of tracers (5% or 10%) shows the three segregation patterns (surface, intermediate, reverse) corresponding to the three types of equilibrium depth. The reversal is smoother than for a single tracer, and happens around the size ratio 4.5, in good agreement with experiments.

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Section: Introductionmentioning

confidence: 99%

Evidence of reverse and intermediate size segregation in dry granular flows down a rough incline

Thomas

d'Ortona

2018

Phys. Rev. E

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“…Size segregation of binary granular mixtures, having an equal volume of large and small particles, is studied in chute flow configuration using DEM simulations for different inclination angles and size ratios. Suitability of the shear rate scaling of the percolation velocity, used by various researchers [3][4][5][6][7][8][9], has been investigated for both symmetric as well as asymmetric segregation flux functions. While the shear rate based scaling of the percolation velocity seems to be reasonable for a given inclination angle, it fails to describe the data when a wide range of inclination angles (and hence shear rates) are considered, i.e., the 'percolation length' used in ref.…”

Section: Resultsmentioning

confidence: 99%

“…2(middle). While the value of κ might depend upon the size ratio and inclination angle [7,9], following ref. [8], we have used a constant value of κ = 0.89 in present study.…”

Section: Percolation Velocity Scalingmentioning

confidence: 99%

“…In these studies, the expression for the segregation flux is symmetric in the species concentration. Recent studies [7][8][9], however, indicate that an asymmetric segregation flux function may be more appropriate to predict the size segregation in binary granular mixtures. In this study, we investigate the shear rate based scaling of the percolation velocity for a binary granular mixture consisting of particles of two different sizes flowing over an inclined plane using DEM simulations.…”

Section: Introductionmentioning

confidence: 99%

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Size Segregation of Binary Granular Mixtures - Towards more appropriate scaling of percolation velocity

Nema

2017

EPJ Web Conf.

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We study size segregation of binary granular mixtures flowing over an inclined plane using DEM simulations. We critically examine the recently proposed scaling of the species percolation velocity with the local shear rate for different inclination angles and size ratios for an equal volume mixture of large and small spherical particles. Our DEM simulations explore a much wider range of inclination angles and shear rates for three different size ratios of large and small particles. Our results suggest that while the scaling of percolation velocity with the shear rate seems to work well for any given inclination angle, this scaling is unable to capture the influence of inclination angle on the segregation. We overcome this limitation and propose a more appropriate way of scaling the percolation velocity. This scaling, when used along with the convection-diffusion equation, is able to predict the steady state segregation of binary mixtures flowing at different inclination angles for different size ratios.

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“…1. For more details regarding the procedure for determining the number of particles and the contact model, please see Tunuguntla et al [16,19].…”

Section: Simulation Setupmentioning

confidence: 99%

Balancing size and density segregation in bidisperse dense granular flows

Tunuguntla

Thornton

2017

EPJ Web Conf.

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Several experimental studies have illustrated a balance between the segregation forces arising due to size-and density-differences. However, no detailed studies have been carried out to quantify this balance. In 2014, by utilising discrete particle simulations, we presented a simple relationship between the particle sizeand density-ratio,ŝ a =ρ , where 'a' determines whether the partial pressure scales with the diameter, surface area or volume of the particle. For a 50:50 mix (in volume) of bidisperse granular mixtures, we found the partial pressure to scale with the volume of the particle, i.e. a = 3. Moreover, there also exists a range of size-and density-ratios that satisfy the relationŝ 3 =ρ , where the bidisperse mixture remains homogeneously mixed. However, in this proceeding, we deviate from the conventional 50:50 mixes and consider a slightly extreme case of mixes, such as the 10:90 (in volume) mixes, which are often found in nature and industries. By doing so we observe that the partial pressure does not scale with the particle volume and, more importantly, the zerosegregation relation is not as simple asŝ a =ρ . However, there does exist a range of size-and density-ratios for which the mixture weakly segregates.

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Comparing and contrasting size-based particle segregation models

Cited by 51 publications

References 49 publications

Evidence of reverse and intermediate size segregation in dry granular flows down a rough incline

Evidence of reverse and intermediate size segregation in dry granular flows down a rough incline

Size Segregation of Binary Granular Mixtures - Towards more appropriate scaling of percolation velocity

Balancing size and density segregation in bidisperse dense granular flows

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