Granular mixing and segregation in zigzag chute flow

Hajra, Suman K.; Shi, Deliang; McCarthy, Joseph J.

doi:10.1103/physreve.86.061318

Cited by 30 publications

(29 citation statements)

References 29 publications

(35 reference statements)

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“…Savage & Lun (1988) found that the percolation velocity of each species is proportional to the concentration of the other species, w p,i ∼ (1 − c i ). The same relation has been used in other studies (Dolgunin et al 1998;Gray & Chugunov 2006;Hajra et al 2012). Accordingly, the local percolation velocity of each species, w p,i , and species volume concentration, c i , are measured from DEM simulations, as described in Appendix A, to investigate the dependence of percolation velocity on particle size ratio and shear rate in bounded heap flow.…”

Section: Percolation Velocitymentioning

confidence: 99%

Modelling size segregation of granular materials: the roles of segregation, advection and diffusion

et al. 2014

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Predicting segregation of granular materials composed of different-sized particles is a challenging problem. In this paper, we develop and implement a theoretical model that captures the interplay between advection, segregation, and diffusion in size bidisperse granular materials. The fluxes associated with these three driving factors depend on the underlying kinematics, whose characteristics play key roles in determining particle segregation configurations. Unlike previous models for segregation, our model uses parameters based on kinematic measures from discrete element method simulations instead of arbitrarily adjustable fitting parameters, and it achieves excellent quantitative agreement with both experimental and simulation results when applied to quasi-two-dimensional bounded heaps. The model yields two dimensionless control parameters, both of which are only functions of physically control parameters (feed rate, particle sizes, and system size) and kinematic parameters (diffusion coefficient, flowing layer depth, and percolation velocity). The Péclet number, P e, captures the interplay of advection and diffusion, and the second dimensionless parameter, Λ, describes the interplay between segregation and advection. A parametric study of Λ and P e demonstrates how the particle segregation configuration depends on the interplay of advection, segregation, and diffusion. The model can be readily adapted to other flow geometries.Key words: Authors should not enter keywords on the manuscript, as these must be chosen by the author during the online submission process and will then be added during the typesetting process (see http://journals.cambridge.org/data/relatedlink/jfm-keywords.pdf for the full list) †

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Section: Percolation Velocitymentioning

confidence: 99%

Modelling size segregation of granular materials: the roles of segregation, advection and diffusion

et al. 2014

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“…In the rolling regime of a tumbler mixer (dense flow), it is a well‐known phenomenon that, under gravity, small particles sink through shear‐generated voids while large particles rise to the top. Below we outline a phenomenological size segregation model proposed by Hajra et al In this model, the segregation velocity is assumed to be proportional to the particle‐size ratio and the average particle diameter so that we get

v_{s} = - K (d_{1} - 〈 d 〉) .

…”

Section: Theorymentioning

confidence: 99%

“…Subscript 1 refers to variables for the smaller particle, while 2 refers to larger particles. K has been assumed to be a constant which has both an intrinsic and a concentration‐dependent component ( K T and K S , respectively) . Expanding

〈 d 〉

and simplifying Eq.…”

Section: Theorymentioning

confidence: 99%

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Validating granular segregation rate models

Liu

McCarthy

2017

AIChE Journal

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One significant hindrance to the development of granular segregation rate models is the inherent difficulty of performing the dynamic experiments required for validation. Here, we seek to overcome this experimental hurdle by establishing an “equilibrium” between segregation and flow perturbation in free surface granular flows and use steady‐state—rather than dynamic—measurements for validation. That is, we combine the segregation rate expressions to be tested with a segregation control framework such that the perturbation rate enables us to infer the segregation rate by measuring simply the steady state extent of segregation. We use periodic flow inversions via an axially located baffle in a tumbler‐type mixer to provide the perturbations that ultimately alter the steady‐state distribution of particles. This work examines the efficacy of existing models for binary segregation driven by either size or density differences. For completeness, we test our model validation framework both computationally and experimentally. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3756–3763, 2017

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“…Despite many differences in particle attributes, differences in size and density are considered to be the most important, see [285,286] and references therein. Similar to the interest shown in understanding monodisperse flows, several experimental studies have attempted to address the issue of size-based particle segregation in rapid dense flows over inclined channels [265,279,[287][288][289][290][291][292][293]. It was in the late 90s' when a two-dimensional discrete element simulation of inelastic disks was carried out to quantitatively describe particle segregation [294].…”

Section: Flows Over Inclined Channels (Chute Flows)mentioning

confidence: 99%

Polydisperse granular flows over inclined channels

Tunuguntla¹

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POLYDISPERSE GRANULAR FLOWS OVER INCLINED CHANNELS DISSERTATIONto obtain the degree of doctor at the University of Twente, on the authority of the rector magnificus, Prof. dr. H. Brinksma, on account of the decision of the graduation committee, to be publicly defended on Friday 9 October 2015 at 16:45 hrs by Deepak Raju Tunuguntla born on the 3rd of November 1986 in Hyderabad, India. Granular materialsEverything seems simpler from a distance. -Gail TsukiyamaMatter exists in a variety of forms, of which granular materials -although simplebehave differently from any of the other standard forms (solid, liquid and gas). For example, a sand castle appears like a solid, which when tumbled upon, crumbles down like an avalanche. On a few occasions, this avalanche takes down the whole castle, whereas sometimes it is confined only to a thin layer on its surface (liquid). In another example, shake up some crushed ice in a cocktail mixer and it behaves like a gas, whereas when trying to pour some salt out of an orifice of a jar, the flow tends to choke and gets clogged at the orifice. Granular material has it all, solid, liquid, gas, plastic flow, glassy, etc. -it can mimic all of these behaviours. Thus exhibiting a prime reason for investing our interest in understanding these simple but, mysterious materials. HistoryOur knowledge of granular matter dates back to an era even before mankind's existence. These materials exist on a range of scales -micron sized to planetary -in a variety of forms, exhibiting multitudes of interesting phenomena. The earliest encounter between man and granular matter happened in the surroundings in which he evolved, i.e. with soil, sand, stones, rocks, etc., but more importantly it was his need for survival that ultimately led to an inevitable bond between humanity and granular matter, existing till today. Historical records indicate that primitive men often settled along the river banks where fresh food was available throughout the year. However, due to climatic changes coupled with migration of primitive tribes, new food gathering methods had to be devised. Man needed to find some way to store the nutrients for periods of time when no fresh food was available. Seeds, such as cereal grains, seemed to be one way to solve 1 1 2 Introduction Figure 1.1: Facsimile of a famous scene from a wall painting on the tomb of Djehutihotep, a pharoah (circa 1932(circa -1842. It illustrates his huge monolithic statue being transported from the quarries. In the front of the statue (near the feet) we see a workman pouring water to lubricate the sand, helping the four rows of workmen, 43 men in each, to haul the sledge smoothy (less friction). The figure is adapted from Dowson [1].the storage problems. Ultimately around 8000 BCE, during neolithic revolution, this seed storage led man towards becoming more agriculturally oriented. Grains were likely among the first cultivated crops. They could be grown relatively easily, farmed in surplus quantities and were suitable for storage in harsh cold winter climat...

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Granular mixing and segregation in zigzag chute flow

Cited by 30 publications

References 29 publications

Modelling size segregation of granular materials: the roles of segregation, advection and diffusion

Modelling size segregation of granular materials: the roles of segregation, advection and diffusion

Validating granular segregation rate models

Polydisperse granular flows over inclined channels

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