Implications of intermittent turbulent bursts for sediment resuspension in a coastal bottom boundary layer: A field study in the western Yellow Sea, China

Yuan, Ye; Wei, Hao; Zhao, Liang; Cao, Yuenan

doi:10.1016/j.margeo.2009.03.023

Cited by 51 publications

(56 citation statements)

References 34 publications

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“…The plots clearly showed that the large contribution of u and w were associated with ejections and sweeps rather than up-acceleration and down-deceleration events. AMCV results were similar with previous studies (Cellino and Lemmin, 2004;Yuan et al, 2009). The distribution of turbulent components for BMCV in the u -w plane reflected a similar pattern which established that resuspension events can occur even below a critical threshold value.…”

Section: Resultssupporting

confidence: 92%

“…Overall, in the time series significant variability and intermittency both in Reynolds stress (u , w ) and sediment resuspension (backscatter) was also revealed. Such intermittent nature of u w was expected and observed previously in the laboratory (Grass, 1974;Sumer and Oguz, 1978;Sumer and Deigaard, 1981;Niño et al, 2003;Schmeeckle, 2015) and in the field (Heathershaw and Thorne, 1985;Drake et al, 1988;Soulsby et al, 1994;Kularatne andPattiaratchi, 2008 andYuan et al, 2009). In more detail, the time series of the AMCV run showed 28 major resuspension events (Fig.…”

Section: Resultssupporting

confidence: 82%

“…Previous studies suggested that the ejections were associated with entrainment of sediment particles into the water column, while sweeps were effective at transporting bedload (Heathershaw, 1979;Soulsby, 1983;Dyer and Soulsby, 1988;Cao, 1997;Keylock, 2007;Yuan et al, 2009). To distinguish between different processes, in this study the term "resuspension" is used for particles initially laying on the bed and at some point lifted into the water column, in contrast to particles permanently in suspension (i.e., washload).…”

Section: Turbulent Burstingmentioning

confidence: 99%

“…Kularatne and Pattiaratchi (2008) performed field experiment in the waveinduced flow environment of Floreat Beach, Perth, Western Australia, and concluded that higher sediment movements were associated with ejections rather than sweeps. In the tidal current environment of western Yellow Sea of China, Yuan et al (2009) conducted experiments and noticed that ejection and sweep events caused most of the observed turbulent sediment flux.…”

Section: Turbulent Burstingmentioning

confidence: 99%

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The influence of turbulent bursting on sediment resuspension under unidirectional currents

et al. 2017

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Abstract. Laboratory experiments were conducted in an open channel flume with a flat sandy bed to examine the role of turbulence on sediment resuspension. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components and acoustic backscatter as a proxy to suspended sediment concentration. Estimates of sediment transport assume that there is a mean critical velocity that needs to be exceeded before sediment transport is initiated. This approach does not consider the turbulent flow field that may initiate sediment resuspension through event-based processes such as the "bursting" phenomenon. In this paper, laboratory measurements were used to examine the sediment resuspension processes below and above the mean critical velocity. The results within a range above and below the measured mean critical velocity suggested that (1) the contribution of turbulent bursting events remained identical in both experimental conditions, (2) ejection and sweep events contributed more to the total sediment flux than up-acceleration and down-deceleration events, and (3) wavelet transform revealed a correlation between the momentum and sediment flux in both test conditions. Such similarities in conditions above and below the measured mean critical velocity highlight the need to re-evaluate the accuracy of a single time-averaged mean critical velocity for the initiation of sediment entrainment.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 82%

Section: Turbulent Burstingmentioning

confidence: 99%

Section: Turbulent Burstingmentioning

confidence: 99%

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The influence of turbulent bursting on sediment resuspension under unidirectional currents

et al. 2017

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“…The largest contributions to stress often occur through ejecting or sweeping motions (Soulsby, 1983). Typically, ejections are associated with entrainment of mass (sediment particles) into suspension, while sweeps are effective at transporting bedload (Cao, 1997;Dyer and Soulsby, 1988;Heathershaw, 1979;Keylock, 2007;Soulsby, 1983;Yuan et al, 2009). While ejections and sweeps reportedly occur in relatively equal proportions near the bed, the former type dominates higher in the water column (Cellino and Lemmin, 2004).…”

Section: Introductionmentioning

confidence: 99%

Wave-induced coherent turbulence structures and sediment resuspension in the nearshore of a prototype-scale sandy barrier beach

Kassem

Thompson

Amos

et al. 2015

Continental Shelf Research

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Abstract:The suspension of sediments by oscillatory flows is a complex case of fluid-particle interaction. The aim of this study is to provide insight into the spatial (time) and scale (frequency) relationships between wave-generated boundary layer turbulence and eventdriven sediment transport beneath irregular shoaling and breaking waves in the nearshore of a prototype sandy barrier beach, using data collected through the Barrier Dynamics Experiment II (BARDEX II). Statistical, quadrant and spectral analyses reveal the anisotropic and intermittent nature of Reynolds' stresses (momentum exchange) in the wave boundary layer, in all three orthogonal planes of motion. The fractional contribution of coherent turbulence structures appears to be dictated by the structural form of eddies beneath plunging and spilling breakers, which in turn define the net sediment mobilisation towards or away from the barrier, and hence ensuing erosion and accretion trends. A standing transverse wave is also observed in the flume, contributing to the substantial skewness of spanwise turbulence. Observed low frequency suspensions are closely linked to the mean flow (wave) properties. Wavelet analysis reveals that the entrainment and maintenance of sediment in suspension through a cluster of bursting sequence is associated with the passage of intermittent slowly-evolving large structures, which can modulate the frequency of smaller motions. Outside the boundary layer, small scale, higher frequency turbulence drives the suspension. The extent to which these spatially varied perturbation clusters persist is associated with suspension events in the high frequency scales, decaying as the turbulent motion ceases to supply momentum, with an observed hysteresis effect. The suspension of sediment in turbulent flows is a complex case of fluid-particle interaction, governed by shear stresses (momentum exchanges) at the bed and within the benthic boundary layer (BBL). Defining the physical processes which dictate the resuspension of sediments in coastal and estuarine settings is fundamental for accurate predictions of bed morphology evolution (Van Rijn et al., 2007), and has profound implications for the biogeochemical processes that shape their local ecology (Thompson et al., 2011). It is also a prerequisite to quantifying erosion and deposition trends, and hence guiding engineering applications such as beach nourishment, defence schemes against erosion and flooding, maintenance of marine infrastructure and waterways, and aggregate dredging. There is a genuine need for better, robust models of suspended sediment transport in the coastal zone (Aagaard and Jensen, 2013). In a vision paper on future research needs in coastal dynamics, Van Rijn et al. (2013) highlighted the pressing need for research to support such models, focusing in particular on sand transport in the shoreface (non-breaking waves), surf and swash zones; employing field and controlled laboratory experiments.The mobilisation of sediments in the nearshore and shoreface is dominated b...

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Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

Fettweis

Baeye

2015

JGR Oceans

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Suspended Particulate Matter (SPM) concentration profiles of the lowest 2 m of the water column and particle size distribution at 2 m above the bed were measured in a coastal turbidity maximum area (southern North Sea) during more than 700 days between 2006 and 2013. The long-term data series of SPM concentration, floc size, and settling velocity have been ensemble averaged according to tidal range, alongshore residual flow direction, and season, in order to investigate the seasonal SPM dynamics and its relation with physical and biological processes. The data show that the SPM is more concentrated in the near-bed layer in summer, whereas in winter, the SPM is better mixed throughout the water column. The decrease of the SPM concentration in the water column during summer is compensated by a higher nearbed concentration indicating that a significant part of the SPM remains in the area during summer rather than being advected out of it. The opposite seasonality between near-bed layer and water column has to our knowledge not yet been presented in literature. Physical effects such as wave heights, wind climate, or storms have a weak correlation with the observed seasonality. The argument to favor microbial activity as main driver of the seasonality lies in the observed variations in floc size and settling velocity. On average, the flocs are larger and thus settling velocities higher in summer than winter.

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Implications of intermittent turbulent bursts for sediment resuspension in a coastal bottom boundary layer: A field study in the western Yellow Sea, China

Cited by 51 publications

References 34 publications

The influence of turbulent bursting on sediment resuspension under unidirectional currents

The influence of turbulent bursting on sediment resuspension under unidirectional currents

Wave-induced coherent turbulence structures and sediment resuspension in the nearshore of a prototype-scale sandy barrier beach

Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

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