An analytical solution for the local suspended sediment concentration profile in tidal sea region

Jung, Kyung Tae; Jin, Jae-Youll; Kang, Hyung-Ku; Lee, Ho Jin

doi:10.1016/j.ecss.2004.07.007

Cited by 10 publications

(7 citation statements)

References 12 publications

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“…To evaluate the time-and space-variation of c and b correctly would require a detailed model of the vertical mixing and redistribution of suspended sediment-for example, using the eddy diffusivity approach recently applied by Jung et al (2004), or the more physically complex and realistic models of Ross and Mehta (1989) or Winterwerp (2001). This lies beyond the current study; however, by analogy with other vertically-averaged sediment transport models (e.g.…”

Section: Governing Equationsmentioning

confidence: 95%

Suspended sediment transport along an idealised tidal embayment: settling lag, residual transport and the interpretation of tidal signals

Pritchard

2005

Ocean Dynamics

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We present semi-analytical solutions for suspended sediment concentration (SSC) and residual sediment transport in a simple mathematical model of a short tidal embayment. These solutions allow us to investigate in some detail the characteristic tidal and semi-tidal variation of SSC and the processes leading to residual sediment transport, including settling and scour lags, the roles of ‘local’ and ‘advective’ contributions, and the presence of internally or externally generated overtides. By interpreting the transport mechanisms in terms of the classic conceptual models of settling lag we clarify how these models may be expressed in mathematical terms. Our results suggest that settling lag is usually a more important process than scour lag, and that a local model which neglects advection may predict the direction of net sediment transport incorrectly. Finally, we discuss our results in the context of other transport processes and morphodynamic feedback

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Section: Governing Equationsmentioning

confidence: 95%

Suspended sediment transport along an idealised tidal embayment: settling lag, residual transport and the interpretation of tidal signals

Pritchard

2005

Ocean Dynamics

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“…However, all these assumptions remain qualitative and overidealized. Another approach to avoid the limitation of using a 1DV model for cohesive sediments is to focus on tide‐dominated periods, during which the effects of C adv ( t ) are reasonably assumed to be small (Jung et al., 2004) because C adv ( t ) is only considered important under wind conditions (Xing & Davies, 2002). However, this assumption may not be reasonable if there is a persistent concentration gradient that is not associated with wind (e.g., Pearson et al., 2019; Weeks et al., 1993).…”

Section: Introductionmentioning

confidence: 99%

Multiscale Superposition and Decomposition of Field‐Measured Suspended Sediment Concentrations: Implications for Extending 1DV Models to Coastal Oceans With Advected Fine Sediments

et al. 2021

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One-dimensional vertical (1DV) sediment diffusion-settling models are practical tools for analyzing sediment transport paths (Pearson et al., 2019; Winterwerp et al., 2011; Yu et al., 2012) and optimizing parameters via reaching best fits with the available observations of suspended sediment concentrations profiles C(t) (e.g., Hill et al., 2003). Such parameters include the eddy diffusivity (D s) and settling velocity (w s) of the suspended sediments, and erosion rate (E r) of the bottom sediments, which are all key parameters for performing theoretical calculations or numerical simulations of coastal processes over a larger domain. However, 1DV models are only valid when the sediments are dominated by local vertical processes. For sandy sediments, an assumption of local resuspension (LR) such that C(t) correlates with the bed shear stress τ(t)∼    2 V t (where V is horizontal velocity) is usually valid and the 1DV models are adequate Abstract One-dimensional vertical (1DV) diffusion-settling models are practical tools for sediment transport analysis of sands, which is mostly a local process. However, for fine sediments, the observed concentrations C(t) can be mixed via horizontal advection (HA) due to the lower settling velocity, which makes the C(t) not necessarily a local process, thus making 1DV models invalid. It is important to determine the qualitative significance of HA or quantitatively separate HA signals when applying 1DV models to environments with advected fine sediments. Here, novel methods are combined to (1) qualitatively identify the physical mechanisms underlying C(t) variations and determine whether HA is significant via multiscale frequency superposition and (2) quantitatively decompose C(t) components according to their physical mechanisms via spectral filter decomposition. In situ observational data of C(t) and concurrent hydrodynamics in the subaqueous Yellow River Delta is employed to analyze the methods' performance. The decomposed signals are reasonable because they can be interpreted in light of other observed physical processes. The results indicated that M2 tidal advection contributed 8.30% by carrying sediments from 1.6 km upstream of the flood tides, M4 and M6 + M8 tidal resuspension contributed 4.16% and 3.96%, respectively, by periodically resuspending a "fluffy layer." Waves resuspended sediments from an erosion center 5 km upstream of the flood tides and contributed to 76.49% of the elevated C(t). The proposed methods can exclude HA signals from the measured C(t) to increase the applicability of 1DV models to environments with advected fines when C(t) and hydrodynamics are measured. Plain Language Summary For fine-grained sediments, measured suspended sediment concentrations can be either resuspended locally or advected by tidal currents from a faraway location. The present paper found that the qualitative intensities of these components can be judged from the temporal pattern of suspended sediment concentrations using frequency superposition analysis. Furthermore, the qu...

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“…In the solution, a constant vertical sediment eddy diffusivity K s is assumed over time and space, in correspondence to several previous analytical approaches (Prandle 1997;Jung et al 2004). However, as shown by Souza et al (2004), in the tidal environments K s will change greatly both in time and in the vertical domain.…”

Section: Discussionmentioning

confidence: 99%

“…For the sake of simplicity, K s is assumed to be constant over time and space in tidal environments (Prandle 1997;Jung et al 2004). …”

Section: Analytical Solutionmentioning

confidence: 99%

“…Because of their inherent complexity, tidal SSC profiles are generally estimated using a variety of numerical approaches (e.g., Wang et al 2005;Stanev et al 2007;van der Molen et al 2009). In some cases, analytical solutions for uniform unsteady flows were achieved by using advanced mathematical tools (Davies 1977;Smith 1977;Lavelle et al 1984;Prandle 1997;Jung et al 2004), but these are relatively complex and hence difficult to implement in practice.…”

Section: Introductionmentioning

confidence: 99%

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Tide-induced vertical suspended sediment concentration profiles: phase lag and amplitude attenuation

Flemming

Gao

2010

Ocean Dynamics

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In tidal environments, the response of suspended sediment concentration (SSC) to the current velocity is not instantaneous, the SSC lagging behind the velocity (phase lag), and the amplitude of SSC variation decreasing with height above the bed (amplitude attenuation). In order to quantitatively describe this phenomenon, a one-dimensional vertical advection-diffusion equation of SSC is derived analytically for uniform unsteady tidal flow by defining a concentration boundary condition using a constant vertical eddy diffusivity and sediment settling velocity. The solution, in simple and straightforward terms, shows that the vertical phase lag increases linearly with the height above the bed, while the amplitude of the SSC variation decreases exponentially with the height. The relationship between the SSC and the normalized current velocity can be represented by an ellipse or a line, depending on the phase lag. The lag of sediment movement or "diffusion/ settling lag" is the mechanism generating the phase lag effect. Field observations used for validation show that the theoretically predicted and the observed curves of the vertical SSC phase lag and amplitude attenuation show reasonable agreement. The procedure proposed in this paper substantially simplifies the modeling of suspended matter transport in tidal flows.

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An analytical solution for the local suspended sediment concentration profile in tidal sea region

Cited by 10 publications

References 12 publications

Suspended sediment transport along an idealised tidal embayment: settling lag, residual transport and the interpretation of tidal signals

Suspended sediment transport along an idealised tidal embayment: settling lag, residual transport and the interpretation of tidal signals

Multiscale Superposition and Decomposition of Field‐Measured Suspended Sediment Concentrations: Implications for Extending 1DV Models to Coastal Oceans With Advected Fine Sediments

Tide-induced vertical suspended sediment concentration profiles: phase lag and amplitude attenuation

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