Particle flow rate in silos under rotational shear

Hernández-Delfin, Dariel; Pongó, Tivadar; To, Kiwing; Börzsönyi, Tamás; Hidalgo, R. C.

doi:10.1103/physreve.102.042902

Cited by 11 publications

(14 citation statements)

References 41 publications

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“…One visible tendency is that the more elongated the particles are, the lower the flow rate for a fixed orifice is. For the case of spheres, we observe a concave line in the plots, which is in agreement with earlier findings [19,36]. This behavior can be explained by either the Beverloo law Q ∝ (D − kd) 5/2 or Q ∝ (1 − α 1 e −D/α2 )D 5/2 type of dependence.…”

Section: A Effect Of Rotational Shear On the Flow Ratesupporting

confidence: 92%

“…For the case of the spheres, we obtain a slight increase with increasing rotational frequency below D = 48 mm or even a weak nonmonotonic behavior (≈ 5% initial drop then ≈ 5% increase) for the larger orifices which we consider. A more in-depth analysis of the behavior of the spheres in this system can be found in our earlier works [19,36]. In contrast, elongated particles show a completely different behavior, regardless the particle aspect ratio, either the orifice size, applying external shear significantly reduces the particle flow rate in the range of examined frequencies.…”

Section: A Effect Of Rotational Shear On the Flow Ratementioning

confidence: 68%

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Discharge of elongated grains in silos under rotational shear

2022

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The discharge of elongated particles from a silo with rotating bottom is investigated numerically. The introduction of a slight transverse shear reduces the flow rate Q by up to 70% compared to stationary bottom, but the flow rate shows a modest increase by further increasing the external shear. Focusing on the dependency of flow rate Q on orifice diameter D, the spheres and rods show two distinct trends. For rods, in the small aperture limit Q seems to follow an exponential trend, deviating from the classical power-law dependence. These macroscopic observations are in good agreement with our earlier experimental findings [Phys. Rev. E 103, 062905 (2021)]. With the help of the coarse-graining methodology we obtain the spatial distribution of the macroscopic density, velocity, kinetic pressure, and orientation fields. This allows us detecting a transition from funnel to mass flow pattern, caused by the external shear. Additionally, averaging these fields in the region of the orifice reveals that the strong initial decrease in Q is mostly attributed to changes in the flow velocity, while the weakly increasing trend at higher rotation rates is related to increasing packing fraction. Similar analysis of the grain orientation at the orifice suggests a correlation of the flow rate magnitude with the vertical orientation and the packing fraction at the orifice with the order of the grains. Lastly, the vertical profile of mean acceleration at the center of the silo denotes that the region where the acceleration is not negligible shrinks significantly due to the strong perturbation induced by the moving wall.

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Section: A Effect Of Rotational Shear On the Flow Ratesupporting

confidence: 92%

Section: A Effect Of Rotational Shear On the Flow Ratementioning

confidence: 68%

Discharge of elongated grains in silos under rotational shear

2022

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“…They become obstacles to the current flowing along the axis of the silo. This is the scenario confirmed in previous studies on silo discharge of spherical grains [25,27]. Here the axes of the pegs at the bottom are mostly horizontal while those pegs in the central current are aligned with their axes vertical.…”

Section: Effects Of Rotation On Flow Ratesupporting

confidence: 88%

“…al. [27] who have confirmed the emergence of a horizontal current at the bottom due to the rotation of the bottom of the silo with respect to the wall. Increasing the rotation rate ω induces a complex change in the velocity field and pack-ing fraction of the material, leading to a non-monotonic (first decreasing then increasing) flow rate with ω.…”

Section: Introductionmentioning

confidence: 87%

Discharge of elongated grains from silo with rotating bottom

To,

Mo,

Pongó

et al. 2021

Preprint

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We study the flow of elongated grains (wooden pegs of length L=20 mm with circular cross section of diameter dc=6 and 8 mm) from a silo with a rotating bottom and a circular orifice of diameter D. In the small orifice range (D/d < 5) clogs are mostly broken by the rotating base, and the flow is intermittent with avalanches and temporary clogs. Here d ≡ ( 3 2 d 2 c L) 1/3 is the effective grain diameter. Unlike for spherical grains, for rods the flow rate W clearly deviates from the power law dependence W ∝ (D−kd) 2.5 at lower orifice sizes in the intermittent regime, where W is measured in between temporary clogs only. Instead, below about D/d < 3 an exponential dependence W ∝ e κD is detected. Here k and κ are constants of order unity. Even more importantly, rotating the silo base leads to a strong -more than 50% -decrease of the flow rate, which otherwise does not depend significantly on the value of ω in the continuous flow regime. In the intermittent regime, W (ω) appears to follow a non-monotonic trend, although with considerable noise. A simple picture, in terms of the switching from funnel flow to mass flow and the alignment of the pegs due to rotation, is proposed to explain the observed difference between spherical and elongated grains. We also observe shear induced orientational ordering of the pegs at the bottom such that their long axes in average are oriented at a small angle θ ≈ 15 • to the motion of the bottom.

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“…With important engineering applications, such as storage and discharge of solids in a silo, transportation of raw materials in a pipe or conveyor belt, Granular Orifice Flow (GOF) has been extensively studied for decades [1][2][3][4][5][6][7][8] . A well-known phenomenon of GOF is that its flow rate is a time-independent constant, and has been used as a timer with accuracy better than that of the clepsydra [9,10] .…”

Section: Introductionmentioning

confidence: 99%

External pressure dependence of granular orifice flow: Transition to Beverloo flow

Peng

Zhou

et al. 2021

Physics of Fluids

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In this paper, we have designed and employed a suspended-wall silo to remove Janssen effect in order to explore directly the local pressure dependence of Granular Orifice Flow (GOF) systematically.We find that as Janssen effect is removed, the flow rate Q changes linearly with the external pressure.The slope α of the linear change decays exponentially with the ratio of the silo size and the size of the orifice Φ/D, which suggests the existence of a characteristic ratio λ (~2.4). When Φ/D > λ, α gradually decays to zero, and the effect of external pressure on the GOF becomes negligible, where the Beverloo law retrieves. Our results show that Janssen effect is not a determining factor of the constant rate of GOF, although it may contribute to shield the top load. The key parameter in GOF is Φ/D. In small Φ/D, the flow rate of GOF can be directly adjusted by the external pressure via our suspended-wall setup, which may be useful to the transportation of granules in microgravity environment where the gravity-driven Beverloo law is disabled.

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Particle flow rate in silos under rotational shear

Cited by 11 publications

References 41 publications

Discharge of elongated grains in silos under rotational shear

Discharge of elongated grains in silos under rotational shear

Discharge of elongated grains from silo with rotating bottom

External pressure dependence of granular orifice flow: Transition to Beverloo flow

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