A simple formula for predicting settling velocity of sediment particles

Song, Zhiyao; Wu, Tingting; Xu, Fumin; Li, Ruijie

doi:10.1016/s1674-2370(15)30017-x

Cited by 148 publications

(56 citation statements)

References 11 publications

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“…For non-cohesive sediments, grain diameters are set. The settling velocities are computed using the formula of Zhiyao et al (2008) and the critical bed-shear stresses follow from the Shields' parameter in the non-cohesive regime (Yalin and . Yellow dots mark the low-water line under the prescribed tidal forcing.…”

Section: Sediment Transportmentioning

confidence: 99%

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

2017

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Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats' morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats' equilibrium as a simplified balance between tidal mechanisms and wave resuspension.

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Section: Sediment Transportmentioning

confidence: 99%

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

2017

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“…We chose a uniform grain size 0.3 mm in diameter, which is a typical size at Sand City beach (Gallagher et al, 2011) and can be suspended in the surf zone . A sinking velocity of the grain w sand = −1.45 × 10 −2 m s −1 was calculated with Zhiyao et al (2008). Therefore, for the DVM model, Equation 3 becomes:…”

Section: Phytoplankton Transport Modelmentioning

confidence: 99%

Mechanisms of Cross-Shore Transport and Spatial Variability of Phytoplankton on a Rip-Channeled Beach

Fujimura¹,

Reniers²,

Paris³

et al. 2018

Front. Mar. Sci.

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We investigated whether cross-shore distributions of coastal phytoplankton to the surf zone are controlled by hydrodynamics and their biological characteristics. Data from a rip-channeled beach indicate that concentrations of phytoplankton are higher in the surf zone than offshore. To examine how phytoplankton is transported toward the shore, we used a coupled biophysical model, comprised of a 3D physical model of coastal dynamics and an individual-based model (IBM) for tracking phytoplankton on the rip-channeled beach. Waves and wind in the biophysical model were parameterized by the conditions during the sampling period. Previous studies indicated that growth rates of phytoplankton can be enhanced by high turbulence, which might contribute to high phytoplankton concentration in the surf zone. Some numerical and laboratory works showed that turbulence can also increase the downward velocity of phytoplankton, which could be carried by onshore bottom currents and remain in the surf zone. Furthermore, we adapted the IBM with the theoretical model of diurnal vertical migration (DVM) for phytoplankton. The theoretical DVM works as follows: in the morning, phytoplankton cells adhere to air bubbles and stay at the surface and close to the shore in the daytime because onshore wind and surface current direction is usually onshore; in the late afternoon, the cells switch their attachment from air bubbles to sand grains and sink to the bottom where the water flow is normally onshore at night. Finally, depth-varying growth of phytoplankton was also incorporated into the DVM module. Simulations using neutral passive particles do not give the expected results of observed patterns. All tested mechanisms, i.e., wind-and wave-driven currents, rip-current circulation, turbulence-driven growth and sinking, DVM, and depth-varying growth, enhanced onshore phytoplankton migration and cell concentrations in the surf zone, indicating that both biological traits and physical factors can be essential to phytoplankton cross-shore transport and spatial variability. Our model is open to be modified and re-parameterized, followed by further analysis and validation, so that it can be more adequate for ecological assessment of coastal areas.

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“…These forces are represented by two Equations. 16 Equation 1 represents the force of gravity acting on the particles while the buoyant force is given by Equation 2.…”

Section: -15mentioning

confidence: 99%

Effects of Continuous Flushing on the Sediment Removal Efficiency in Settling Basins of Small Scale Irrigation Projects; A Case Study of Kiriku-Kiende Irrigation Project, Embu County, Kenya

Namu

Raude

Mutua

2017

IJH

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Effects of continuous flushing on the sediment removal efficiency in settling basins of small scale irrigation projects; a case study of kiriku-kiende irrigation project, embu county, kenya Submit Manuscript | http://medcraveonline.com IntroductionSurface irrigation is a widely used farming system for crop production as it requires less skilled labour and involves less operational cost. Surface irrigation systems contributed to about 90% of the world's crop land irrigation promoting furrow irrigation as the main application method.1 However, poor design and management, non-uniformity of water application, and over-irrigation featured in surface irrigation are responsible for inefficient irrigation, leading to wastage of water, water logging, salinization, and pollution of surface and ground water resources.2 Irrigated agriculture is under serious risk due to substantial soil losses from highly erodible soils.3−5 Irrigated agriculture has been faced with challenges such as sediment loading in the river basins, settling tanks and dams.6 Many factors such as surface and solids loading rates, tank type, solids removal mechanism, inlet design, weir placement and loading rate affect the capacity and performance of a settling tank. 7 The management of sediments in river basins and waterways has been an important issue for water managers throughout the history as from the ancient Egyptians managing sediment on floodplains.8 Currently, water managers are faced with similar challenges mainly resulting in siltation of water reservoirs, reduced capacity of water transport, annual irrigation acreage reduction and high maintenance cost for an irrigation project. 9,10Kenya is not exempted from the dangers posed by sedimentation and siltation in her water bodies. According to, 11 a high proportion of sediments generated in the catchment areas is delivered through soil erosion to the rivers and lakes. Effective management of sediments from rivers during irrigation water abstraction by use of settling basins has become increasingly important from an economic and environmental perspective. Many factors such as surface and solids loading rates, tank type, solids removal mechanism, inlet design, weir placement and loading rate affect the capacity and performance of a settling tank.7 Sediments in irrigation network causes clogging and blocking of irrigation structures. This contributes to overall low irrigation water delivery to the farms. This study was to examine the effect of continuous sediment flushing versus desilting. This would form a basis for designers of settling basin for consideration of continuous flushing for eventual increase of the overall efficiency of irrigation systems. In Kenya, smallholder irrigation development is one of the key strategies for land use intensification with expected positive effects on rural incomes and poverty alleviation. About 20% (106,600 ha) of the potential irrigable land is already under irrigation where 50% (53,300) of this area is under smallholder irrigation. 12−14Table 1 presents the ...

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A simple formula for predicting settling velocity of sediment particles

Cited by 148 publications

References 11 publications

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

Mechanisms of Cross-Shore Transport and Spatial Variability of Phytoplankton on a Rip-Channeled Beach

Effects of Continuous Flushing on the Sediment Removal Efficiency in Settling Basins of Small Scale Irrigation Projects; A Case Study of Kiriku-Kiende Irrigation Project, Embu County, Kenya

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