Inception of Sediment Transport

Yalin, M. Selim; Karahan, Emin

doi:10.1061/jyceaj.0005306

Cited by 296 publications

(81 citation statements)

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“…Note that, for such conditions, both thresholds are approximately equivalent to each other and Θ t (Clark et al., 2017; Pähtz & Durán, 2018a). Furthermore, flume measurements of the visual initiation threshold for subaqueous bedload by Karahan (1975, K75, s ≃ 2.65), Fernandez Luque and van Beek (1976, FLB76, s ∈ (1.3, 4.6)), and Yalin and Karahan (1979, YK79t, s ≃ 2.65) are shown (closed symbols in Figure 5c), where critical conditions are defined by a critical value of a proxy characterizing the state of transport, such as a critical value of the nondimensionalized bed sediment entrainment rate (Paphitis, 2001, Equation 7). It has been argued that the resulting threshold is close to Θ t because such and similar critical transport conditions are associated with an abrupt sharp transition in the behavior of Q * as a function of Θ (Pähtz et al., 2020).…”

Section: Resultsmentioning

confidence: 99%

“…For NST driven by laminar flows, flume measurements of the visual initiation threshold by Yalin and Karahan (1979, YK79l, s ∈ (1.9, 2.3)) and Loiseleux et al. (2005, L05, s ∈ (2.1, 2.5)) and of the visual cessation threshold by Ouriemi et al.…”

Section: Resultsmentioning

confidence: 99%

“…(2019), Pähtz and Durán (2018a), Pähtz and Durán (2020), Meyer‐Peter and Müller (1948, pp. 39–64), Karahan (1975), Fernandez Luque and van Beek (1976), Yalin and Karahan (1979), Smart and Jaeggi (1983), Loiseleux et al. (2005), Ouriemi et al.…”

Section: Data Availability Statementmentioning

confidence: 99%

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Unified Model of Sediment Transport Threshold and Rate Across Weak and Intense Subaqueous Bedload, Windblown Sand, and Windblown Snow

et al. 2021

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• Unified model simultaneously captures sediment transport threshold and rate data 10 across conditions in water and air within a factor of 2 11 • Model supports the recent numerical result that the threshold and rate of equi-12 librium aeolian saltation are insensitive to soil cohesion 13 • Model challenges the classical prediction that the transport threshold for a lon-14 gitudinally sloped bed depends on the angle of repose 15

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Unified Model of Sediment Transport Threshold and Rate Across Weak and Intense Subaqueous Bedload, Windblown Sand, and Windblown Snow

et al. 2021

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“…G can be interpreted as a Reynolds number based on the settling velocity; G 2/3 can also be thought of as a dimensionless grain diameter. This threshold has been extensively measured for incipient subaqueous bedload, varying grain diameter and fluid viscosity (33,34). In that case, the average threshold data compare quantitatively with a simplified model based on a free body diagram on a single grain (35).…”

Section: Dimensionless Numbers For Sediment Transportmentioning

confidence: 92%

A lower-than-expected saltation threshold at Martian pressure and below

Andreotti

Claudin

Iversen

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Aeolian sediment transport is observed to occur on Mars as well as other extraterrestrial environments, generating ripples and dunes as on Earth. The search for terrestrial analogs of planetary bedforms, as well as environmental simulation experiments able to reproduce their formation in planetary conditions, are powerful ways to question our understanding of geomorphological processes toward unusual environmental conditions. Here, we perform sediment transport laboratory experiments in a closed-circuit wind tunnel placed in a vacuum chamber and operated at extremely low pressures to show that Martian conditions belong to a previously unexplored saltation regime. The threshold wind speed required to initiate saltation is only quantitatively predicted by state-of-the art models up to a density ratio between grain and air of 4×105 but unexpectedly falls to much lower values for higher density ratios. In contrast, impact ripples, whose emergence is continuously observed on the granular bed over the whole pressure range investigated, display a characteristic wavelength and propagation velocity essentially independent of pressure. A comparison of these findings with existing models suggests that sediment transport at low Reynolds number but high grain-to-fluid density ratio may be dominated by collective effects associated with grain inertia in the granular collisional layer.

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“…Shields (1936) developed an empirical approach that involves the dimensionless shear stress as a function of the grain size and Reynolds number. The work was updated by Yalin and Karahan (1979) using carefully scrutinized, available experimental data and subsequently improved further by Soulsby (1997). In practice, shear stress is also determined in the field or in the laboratory using flume tests, submerged jetindex tests, the erosion function apparatus, cylindrical erosion tests, or other test methods (e.g., Hanson and Simon 2001;Briaud 2008;Chang et al, 2011;Zhang et al, 2016;Zhu and Zhang 2016).…”

Section: Introductionmentioning

confidence: 99%

Erosion Rate of Lateral Slope Deposit Under the Effects of Different Influencing Factors

Guo

Zhan³

et al. 2021

Front. Earth Sci.

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Lateral slope deposits along a channel represent an important source of material for initiation and development of debris flows/floods that are typically observed in many headwater tributaries. This study found that the failure process of such a deposit reflects combined interaction between external hydrodynamic factors (inflow discharge and channel slope) and internal factors (compactness and fine particle content). The erosion process comprises two stages: runoff erosion toward the toe of the deposit body and soil failure owing to gravity. Spatially, the erosion rate is distributed unevenly across the deposit; the highest value occurs at the section close to the middle of the deposit, on the upstream face. Temporally, the erosion rate decreases exponentially. Overall, the average erosion rate decreases (increases) with bulk density (inflow discharge and channel slope). However, a slope of 7 is a threshold at which the tendency of the erosion rate in relation to the fine particle content differs. In comparison with the other three influencing factors, the effect of the fine particle content is much smaller. Although the bulk density of the deposit imposes the most significant effect, it is of the same order as that of both inflow discharge and channel slope. As the failure process can be summarized as repeated runoff scouring of the toe of the deposit, deposit failure, and entrainment of the failure body by runoff, we proposed a calculation method for the total time required for a complete lateral erosion process, and validation of the calculation suggested its reasonability. The findings of this study enhance the understanding of the mechanism of lateral soil deposit failure, which could help improve runoff-induced debris flood forecasting in headwater regions of mountainous catchments.

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Inception of Sediment Transport

Cited by 296 publications

References 0 publications

Unified Model of Sediment Transport Threshold and Rate Across Weak and Intense Subaqueous Bedload, Windblown Sand, and Windblown Snow

Unified Model of Sediment Transport Threshold and Rate Across Weak and Intense Subaqueous Bedload, Windblown Sand, and Windblown Snow

A lower-than-expected saltation threshold at Martian pressure and below

Erosion Rate of Lateral Slope Deposit Under the Effects of Different Influencing Factors

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