Generation of net sediment transport by velocity skewness in oscillatory sheet flow

Chen, Xin; Li, Yong; Chen, Genfa; Wang, Fujun; Tang, Xuelin

doi:10.1016/j.advwatres.2017.11.006

Cited by 16 publications

(3 citation statements)

References 32 publications

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“…ϕ ( t ) /ϕ m at the crest becomes plump and flattens when n decreases from 4 to 1, when the phase-lag and α 1 = [0.04, 0.53, 0.82, 0.92] are increased by U m . Generally, the curves can be approximated by Sign( U )| U/U m | n with n = 1 for α 1 >0.8, n = 2 for α 1 = 0.4–0.5 and n = 3–5 for α 1 <0.2. n for Eq (7) is slightly larger than that in [ 37 ] and can extend to 3–5 due to the δ that can present the net current and extra net sediment transport in asymmetric flow.…”

Section: Analytical Modelmentioning

confidence: 87%

“…The wave boundary layer thickness δ B = 4.6 δ is directly obtained in Eq (6) , where a large δ B corresponds to a small shear stress and transport rate for the same flow [ 11 ]. The asymmetric δ B generates net current and extra net sediment transport [ 37 ]. The following result is taken from the imaginary part of Eq (6) , that is ϕ is the instantaneous transport rate that related to the bottom velocity phase-lead, boundary layer thickness and erosion depth.…”

Section: Analytical Modelmentioning

confidence: 99%

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Instantaneous sediment transport model for asymmetric oscillatory sheet flow

Chen

et al. 2017

PLoS ONE

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On the basis of advanced concentration and velocity profiles above a mobile seabed, an instantaneous analytical model is derived for sediment transport in asymmetric oscillatory flow. The applied concentration profile is obtained from the classical exponential law based on mass conservation, and asymmetric velocity profile is developed following the turbulent boundary layer theory and the asymmetric wave theory. The proposed model includes two parts: the basic part that consists of erosion depth and free stream velocity, and can be simplified to the total Shields parameter power 3/2 in accordance with the classical empirical models, and the extra vital part that consists of phase-lead, boundary layer thickness and erosion depth. The effects of suspended sediment, phase-lag and asymmetric boundary layer development are considered particularly in the model. The observed instantaneous transport rate proportional to different velocity exponents due to phase-lag is unified and summarised by the proposed model. Both instantaneous and half period empirical formulas are compared with the developed model, using extensive data on a wide range of flow and sediment conditions. The synchronous variation in instantaneous transport rate with free stream velocity and its decrement caused by increased sediment size are predicted correctly. Net transport rates, especially offshore transport rates with large phase-lag under velocity skewed flows, which existing instantaneous type formulas failed to predict, are predicted correctly in both direction and magnitude by the proposed model. Net sediment transport rates are affected not only by suspended sediment and phase-lag, but also by the boundary layer difference between onshore and offshore.

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Section: Analytical Modelmentioning

confidence: 87%

Section: Analytical Modelmentioning

confidence: 99%

Instantaneous sediment transport model for asymmetric oscillatory sheet flow

Chen

et al. 2017

PLoS ONE

Self Cite

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show abstract

“…The uniform and non-uniform sediment transports under steady flow condition have been extensively studied [9][10][11][12]. Besides, some numerical simulations were carried out under unsteady flow condition [13][14][15][16]. The above studies were mostly focused on uniform sediment under steady flow conditions.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Uniform and Mixed Bed-Load Sediment Transport under Unsteady Flow

et al. 2020

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The scouring and deposition of sediment caused by unsteady flows (e.g., storm waves and floods) produces many secondary disasters. The resultant bed-load movement exhibits different transport laws compared with that by steady flow. In this study, the flume experiments were performed to study the bed-load movement under unsteady flow with different velocity skewness. The movement of uniform and non-uniform non-cohesive sediment under unsteady flow as well as the influence of the steady and unsteady flow on sediment transport rate are compared. Additionally, the non-uniform sediment transport formula of fine-to-coarse particle diameter ratio was investigated. The results showed that the sediment transport rate between uniform and non-uniform sand under the same median diameter is different. The non-uniform sediment transport rate is 1.27-, 3.19-, and 0.68-times as large as that in uniform sediment under d50 = 0.664, 1.333, and 2.639 mm under unsteady flow, respectively. For non-uniform sand, the transport rate of non-uniform sand with a larger adjacent particle size ratio (δ = 0.29) was 1.31-times greater than that of the non-uniform sand with a smaller adjacent particle size ratio (δ = 0.50). Moreover, theoretical deduction was carried out and the incipient sediment motion was analyzed from the force mechanism. A new unsteadiness parameter based on the acceleration concept was proposed. The relationship between the travel distance and velocity skewness of sediment particles was set up. The experimental results and theoretical analysis showed that sediment under unsteady flow were easier to start and transport than those under steady flow in the same flow effect. The travel distance of sediment particles was longer under unsteady flow than that under steady flow.

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Uniform fertilization method based on differential pressure tank with optimal fertilizer concentration and constant fertigation flux

Chen

2021

Irrig Sci

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Generation of net sediment transport by velocity skewness in oscillatory sheet flow

Cited by 16 publications

References 32 publications

Instantaneous sediment transport model for asymmetric oscillatory sheet flow

Instantaneous sediment transport model for asymmetric oscillatory sheet flow

Experimental Study on Uniform and Mixed Bed-Load Sediment Transport under Unsteady Flow

Uniform fertilization method based on differential pressure tank with optimal fertilizer concentration and constant fertigation flux

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