Grain shape effects in bed load sediment transport

Deal, Eric; Venditti, Jeremy G.; Benavides, Santiago J.; Bradley, R. W.; Zhang, Qiong; Kamrin, Ken; Perron, J. Taylor

doi:10.1038/s41586-022-05564-6

Cited by 46 publications

(28 citation statements)

References 53 publications

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“…Some reasons for the underestimation of the average sediment transport rates in the simulations can be related to the shape of the particles (natural gravel in the experiments, spheres in the simulations (Deal et al. 2023, cf. )), to experimental uncertainties as, for instance, additional moment added by the sediment feeding system, and to the strong nonlinear dependence of sediment transport rates on boundary conditions and the wall shear stresses.…”

Section: Resultsmentioning

confidence: 99%

Particle-resolved simulation of antidunes in free-surface flows

et al. 2023

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The interaction of supercritical turbulent flows with granular sediment beds is challenging to study both experimentally and numerically. This challenging task has hampered advances in understanding antidunes, the most characteristic bedform of supercritical flows. This article presents the first numerical attempt to simulate upstream-migrating antidunes with geometrically resolved particles and a liquid–gas interface. Our simulations provide data at a resolution higher than laboratory experiments, and they can therefore provide new insights into the mechanisms of antidune migration and contribute to a deeper understanding of the underlying physics. To manage the simulations’ computational costs and physical complexity, we employ the cumulant lattice Boltzmann method in conjunction with a discrete element method for particle interactions, as well as a volume-of-fluid scheme to track the deformable free surface of the fluid. By reproducing two flow configurations of previous experiments (Pascal et al., Earth Surf. Process. Landf., vol. 46, issue 9, 2021, pp. 1750–1765), we demonstrate that our approach is robust and accurately predicts the antidunes’ amplitude, wavelength and celerity. Furthermore, the simulated wall shear stress, a key parameter governing sediment transport, is in excellent agreement with the experimental measurements. The highly resolved data of fluid and particle motion from our simulation approach open new perspectives for detailed studies of morphodynamics in shallow supercritical flows.

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Section: Resultsmentioning

confidence: 99%

Particle-resolved simulation of antidunes in free-surface flows

et al. 2023

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“…4), 𝜌𝜌 = characteristic particle size (typically expressed as a grain diameter, and the subscript 'c' denotes critical and refers to the shear stress value above which a particle would start moving (incipient motion). It has long been recognized that particle shape also affects its mobility and recent work has provided new insights into its implications (e.g., Cassel et al, 2021;Deal et al, 2023). To account for grain shape effects in bed load sediment mobility, Deal et al, (2023) introduced a shape-corrected Shields number (𝐶𝐶 * 𝜇𝜇 * ⁄ )𝜏𝜏 𝑐𝑐 * where 𝐶𝐶 * is an effective drag coefficient, and 𝜇𝜇 * is an average bulk friction coefficient.…”

Section: Basic Principles Of Sediment Transportmentioning

confidence: 99%

“…It has long been recognized that particle shape also affects its mobility and recent work has provided new insights into its implications (e.g., Cassel et al, 2021;Deal et al, 2023). To account for grain shape effects in bed load sediment mobility, Deal et al, (2023) introduced a shape-corrected Shields number (𝐶𝐶 * 𝜇𝜇 * ⁄ )𝜏𝜏 𝑐𝑐 * where 𝐶𝐶 * is an effective drag coefficient, and 𝜇𝜇 * is an average bulk friction coefficient. This modified Shields number also applies when treating plastic as a sediment.…”

Section: Basic Principles Of Sediment Transportmentioning

confidence: 99%

“…shapes have been found to settle differently across different flow regimes (Francalanci et al, 2021), and bedload sediment transport is affected by particle shape (e.g., Deal et al, 2023), providing important insight into a particle characteristic that sedimentology had not sufficiently considered. Material such as paint flakes seem to align with existing models (Enders et al, 2019), but other materials, even in simple shapes, may not (Chubarenko & Stepanova, 2017;Khatmullina & Chubarenko, 2019;Waldschläger & Schüttrumpf, 2019b;Mendrik et al, 2023), and films and fibres introduce additional uncertainty due to their properties, particularly particles that change their shape when settling (Zhang & Choi, 2021;Choi et al, 2022).…”

Section: Implications For Sediment and Plastic Transport Modellingmentioning

confidence: 99%

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Plastic as a Sediment – A Universal and Objective practical solution to growing ambiguity in plastic litter classification schemes

Russell¹,

Pohl²,

Fernández³

2023

Preprint

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There is a universal and growing challenge of ambiguity in plastic classification schemes, which affects the predictability of plastic accumulation in all environments world-wide. Plastic pollution is an ever-growing global issue, and understanding plastic items and their sedimentological relationship is a solution to this increasing concern. Definitions of micro- meso- and macro- plastic is inconsistent between studies, as are categories of plastic, and the properties recorded. This is understandable because every project has a different objective, but the consequence is that different studies are not laterally relatable. It is widely agreed that as a community, we need a system that has room for specialism of study but has an objective basis that can allow for inter-project and inter-disciplinary collaborations. By considering plastic as a sediment, we can outline an objective and quantifiable classification scheme that builds on the principles of sedimentology for use in plastic studies, such that we can better understand why plastics accumulate where they do. This is importantly not just another classification scheme, but a philosophically grounded solution to a long-standing challenge that is set to be of increasing significance. Additionally, whilst these advances may be of immediate usefulness to the scientist interested in plastic transport and accumulation, the environmental scientist or biologist will find that these philosophies and classification scheme will aid to quantitatively support and compliment aligning data. Through this, our new plastic and sediment environment can be further understood both spatially and temporally, and connected to other studies. We outline the key philosophies of sedimentology and use these to: i) unify and define plastic size classification from nano-scale to mega- and introduce giga- scale; ii) we outline a shape classification that can tackle simple through to complex shapes; iii) we discuss and demonstrate the importance of total density over polymer density; and iv) we discuss the importance of material properties. In using this classification scheme, we can relate any plastic item to any other item, and to itself over time. This manuscript contains a summary and worksheet that can be used in the field or in a laboratory to utilise this scheme and present objectively comparable results. We are confident that the philosophies presented here will be of use to the plastic research community, such that we can integrate plastic studies with longstanding and deeply understood sedimentological knowledge, thereby enhancing our understanding of plastic routing and accumulation in the environment.

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“…However, most formulations of bedload transport in rivers assume spherical grains that do not represent natural sediment. Only recently has grain shape been shown to affect fluvial sediment transport via changes in fluid drag (53,54) and interactions with the granular bed (53,55). The role of grain shape in controlling granular segregation processes in natural fluid flows has been unexplored.…”

Section: Anisotropy and The Approach To Shear Jammingmentioning

confidence: 99%

How particle shape affects granular segregation in industrial and geophysical flows

Cunez¹,

Patel²,

Glade³

2023

Preprint

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Industrial and environmental granular flows commonly exhibit a phenomenon known as ``granular segregation," in which grains separate according to physical characteristics (size, shape, density), interfering with industrial applications (cement mixing, medicine and food production) and fundamentally altering the behavior of geophysical flows (landslides, debris flows, pyroclastic flows, riverbeds). While size-induced segregation has been well studied, the role of grain shape is not well understood. Here we conduct numerical experiments to investigate how grain shape affects granular segregation due to grain-grain and grain-fluid interactions. To isolate the former, we compare dry, bidisperse mixtures of spheres alone with mixtures of spheres and cubes in a rotating drum. Results show that while segregation generally increases with particle size ratio, the presence of cubes decreases segregation levels compared to cases with only spheres. Further, we find hysteresis in segregation trends with size ratio; segregation is lowest when the small grains are cubic as they approach a jammed state with reduced mobility. We find similar hysteresis in simulations of a shear-driven coupled fluid-granular flow (e.g., a riverbed), demonstrating that this phenomenon is not unique to rotating drums; however, in contrast to the dry system, we find that total segregation increases in the presence of cubic grains, and fluid drag effects can qualitatively change segregation trends. Our findings demonstrate competing shape-induced segregation patterns in wet and dry flows—independently from grain size controls—with implications for many industrial and geophysical processes.

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Grain shape effects in bed load sediment transport

Cited by 46 publications

References 53 publications

Particle-resolved simulation of antidunes in free-surface flows

Particle-resolved simulation of antidunes in free-surface flows

Plastic as a Sediment – A Universal and Objective practical solution to growing ambiguity in plastic litter classification schemes

How particle shape affects granular segregation in industrial and geophysical flows

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