Experiment inspired numerical modeling of sediment concentration over sand–silt mixtures

Yao, Peng; Su, Min; Wang, Zheng Bing; Rijn, Leo C. van; Zhang, Changkuan; Chen, Yongping; Stive, M.J.F.

doi:10.1016/j.coastaleng.2015.07.008

Cited by 32 publications

(69 citation statements)

References 35 publications

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“…Experiments have shown that there is a distinct interface between the HCL near the bottom and the clear water in the upper part under wave conditions, as shown in Figure 1-2 (Lamb and Parsons, 2005) and Figure 1-3 (Yao et al, 2015). In this study the HCL is defined as the higher concentration layer below where the gradient of sediment concentration changes abruptly in the upper part.…”

Section: Behaviour Of Sediments With Different Grain Sizesmentioning

confidence: 78%

“…Stevens (1991) proposed 16 μm to be the division between sediments that flocculate significantly. Some experiments (Li, 2014;Yao et al, 2015;Zhou and Ju, 2007) showed that the grain size of 45  m to 110  m shared similar suspension behaviour under wave-current conditions. Some scholars defined the silty coast with medium grain size of 30  m to 125  m and the clay percentage less than 25%, to be differentiated with sandy coast and muddy coast .…”

Section: Behaviour Of Sediments With Different Grain Sizesmentioning

confidence: 96%

“…Sediment suspension is limited by the high oscillatory motion, and the sediment concentration near the bottom is much higher than that in the upper part. The HCL has been found in laboratory experiments (Dohmen Janssen et al, 2001;Yao et al, 2015) and field observations (Te Slaa et al, 2013). Some literature (Kineke et al, 1996;Trowbridge and Kineke, 1994) defines high concentration at the elevation where the concentration c = 10 kg/m 3 , or c = 21 kg/m 3 by Winterwerp (1999).…”

Section: Behaviour Of Sediments With Different Grain Sizesmentioning

confidence: 98%

“…Erosion tests have suggested that silt-enriched mixtures exhibit cohesive-like behaviour (Roberts et al, 1998), but flocculation has not been observed based on settling experiments on silt (with clay contents less than 10%) (Te Slaa et al, 2015;Yao et al, 2015). Silt is often referred to as pseudo-cohesive or semi-cohesive sediment, to be differentiated from non-cohesive or cohesive materials.…”

Section: Behaviour Of Sediments With Different Grain Sizesmentioning

confidence: 99%

“…Due to its special behaviour, this kind of sediment has drawn much attention from researchers in recent years, such as studies on the hindered settling (Te Slaa et al, 2015), sediment movement and reference concentration (Yao et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Modelling and Analysis of Fine Sediment Transport in Wave-Current Bottom Boundary Layer

Zuo¹

2018

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Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers, the author nor IHE Delft for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. A pdf version of this work will be made available as Open Access via http://repository.tudelft.nl/ihe. This version is licensed under the Creative Commons To my family AbstractThe evolution and utilization of estuarine and coastal regions are greatly restricted by sediment problems. Inspired by the Caofeidian sea area in Bohai Bay, China, this study aims to better understand silty sediment transport under combined action of waves and currents, especially in the wave-current bottom boundary layer (BBL), and to improve our modelling approaches in predicting estuarine and coastal sediment transport.Field observations were carried out in northwestern Caofeidian sea area of Bohai Bay and field data were collected on several other silt-dominated coasts. Analysis shows that silt-dominated sediments are sensitive to flow dynamics: the suspended sediment concentrations (SSCs) increase rapidly under strong flow dynamics (i.e., waves or strong tidal currents which can stir up sediments), and high concentrations cause heavy sudden back siltation in navigation channels. In the following, details of silty sediment transport are studied, focusing on the BBL and high concentration layer (HCL).From laboratory experiments and theoretical analysis, an expression for sediment incipient motion is proposed for silt-sand sediment under combined wave and current conditions. The Shields number was revised by adding the cohesive force and additional static pressure, leading to an extended Shields curve.To study the HCL, a process based 1DV model was developed for flow-sediment dynamics near the bed in combined wave-current conditions. Based on the physical processes, special approaches for sediment movement were introduced, including approaches for different bed forms (rippled bed and 'flat-bed'), hindered settling, stratification effects, mobile bed effects, reference concentration and critical shear stress. The HCL was simulated and sensitivity analysis was carried out by the 1DV model on factors that impact the sediment concentration in the HCL. The results show that the HCL is affected by both flow dynamics and bed forms; the thickness of the HCL is about twice the height of the wave boundary layer; bed forms determine the shape of the concentration profile near the bottom, and flow dynamics determine the magnitude. For finer sediment, stratification effects and mobile bed effects impact the sediment concentration greatly.Finally, based on the 1DV model, the formulations of the mean sediment concentration profile of silty sediments were studied. By solving the time-averaged diffusion equation for SSC and considering the effects of bed forms, stratification and hindered settling, expressions for time-averaged SSC profile...

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Section: Behaviour Of Sediments With Different Grain Sizesmentioning

confidence: 78%

Section: Behaviour Of Sediments With Different Grain Sizesmentioning

confidence: 96%