Axial segregation of granular flows in a horizontal rotating cylinder

Nakagawa, Masami

doi:10.1016/0009-2509(94)e0086-6

Cited by 104 publications

(48 citation statements)

References 3 publications

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“…It is claimed that more bands appear when more small particles are used [5], and that more bands appear when the rotation rate is slower [7]. Recently, MRI studies have shown that there exist subsurface bands that may not be visible from the surface [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…After a few hundred to a few thousand rotations, an apparently stable array of axial bands of roughly equal spacing is formed. Bands may merge or split on long time scales, but the general tendency is towards merging [5,7,13,15]. With very extended rotation time, some experiments show that the bands exhibit a remarkably long period of metastability, but eventually all merge and finally achieve complete segregation, where the two species occupy opposite ends of the tube.…”

Section: Introductionmentioning

confidence: 99%

“…In 1939, Oyama noticed that a binary mixture of large-and small-grained sand segregated into axial bands when tumbled in a horizontal "drum mixer". [1] After a hiatus of several decades, this counterintuitive phenomenon has captured the attention of many researchers, [2][3][4][5][6][7][8][9][10][11][12][13][14][15] and it has become something of a standard problem in the study of granular materials.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of granular segregation patterns in a long drum mixer

et al. 1998

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We have studied the early time evolution of granular segregation patterns in a horizontal rotating cylinder partially filled with a sand/salt mixture. The growth of concentration fluctuations starting from premixed initial conditions was analyzed using Fourier techniques. In one mixture, we observed generally merging dynamics in the segregated bands up to the onset of saturation. At the threshold of saturation, we found a spectrum of wavelengths with a broad peak. The peak position was nearly independent of the tube rotation rate.The overall growth rate of Fourier modes had a maximum at a particular value of the angular rotation frequency. In a slightly different mixture, we observed transient traveling waves when the larger grains were in the majority. We measured the wave speed as a function of several parameters using presegregated initial conditions to launch waves of various wavelengths.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamics of granular segregation patterns in a long drum mixer

et al. 1998

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“…This pattern is inverted for lower fill fractions so that small particles accumulate near the poles with a band of large particles at the equator [17]. We note that multiple bands of small and large particles occur for bidisperse mixtures in long rotating cylindrical tumblers, which are used in applications for materials ranging from foodstuffs to mining to cement, typically after O (10) to O(100) rotations and having a wavelength of about one tumbler diameter [18] under a wide range of conditions [18][19][20][21][22][23][24][25]. In the cylindrical tumbler case, however, large particles segregate near the flat end walls of the tumbler [18,23,26], as a consequence of radial segregation combined with the nonuniform axial distribution of velocity in the flowing layer due to friction at the endwall [27].…”

Section: Introductionmentioning

confidence: 99%

Influence of rough and smooth walls on macroscale granular segregation patterns

2016

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Size bidisperse granular materials in a spherical tumbler segregate into two different patterns of three bands with either small particles at the equator and large particles at the poles or vice versa, depending upon the fill level in the tumbler. Here we use discrete element method (DEM) simulations with supporting qualitative experiments to explore the effect of the tumbler wall roughness on the segregation pattern, modeling the tumbler walls as either a closely packed monolayer of fixed particles resulting in a rough wall, or as a geometrically smooth wall. Even though the tumbler wall is in contact with the flowing layer only at its periphery, the impact of wall roughness is profound.Smooth walls tend toward a small-large-small (SLS) band pattern at the pole-equator-pole at all but the highest fill fractions; rough walls tend toward a large-small-large (LSL) band pattern at all but the lowest fill fractions. This comes about because smooth walls induce poleward axial drift of small particles and an equator-directed drift for large particles, resulting in an SLS band pattern.On the other hand, rough walls result in both sizes of particles moving poleward at the surface of the flow, but due to radial segregation, small particles percolate lower in the flowing layer where there is a return drift toward the equator while large particles remain at the surface near the pole,

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“…Nakagawa is probably the first person who pointed out the importance of the end walls in axial segregation band formation (Nakagawa, 1994). The angle of repose of the particles next to the end wall is different to that in the bulk and particle motion in the axial direction accelerates, causing the formation of the segregation bands.…”

Section: Introductionmentioning

confidence: 99%

Controlling of Segregation in Rotating Drums by Independent End Wall Rotations

Kuo

Tseng

Huang

2016

KONA

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We present in this study that particle segregation in rotating drums can be controlled by end wall rotations. While the end wall rotational speed dominates the time required for reaching the steady state, the rotational direction of the end walls determines the segregation patterns and the shearing zone size. New segregation patterns with two well-mixed regions close to the end walls are observed in the drums with the end wall rotates in the direction opposite to the cylindrical wall. The end wall rotation causes the formation of the local valley and hill next to the wall. Particles flow into the valley and down the hill causing the formation of the convective flow cell at bed surface. It is the difference of the axial velocities between the large particles and small particles close to the end walls separating the particles of difference sizes in the axial direction. The controlling of the end wall roughness and rotating directions effectively enlarge the size of the end wall shearing zone; resulting segregation patterns which are different from the previous simple segregation band patterns.

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Axial segregation of granular flows in a horizontal rotating cylinder

Cited by 104 publications

References 3 publications

Dynamics of granular segregation patterns in a long drum mixer

Dynamics of granular segregation patterns in a long drum mixer

Influence of rough and smooth walls on macroscale granular segregation patterns

Controlling of Segregation in Rotating Drums by Independent End Wall Rotations

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