Turbulent transfer mechanism in sediment‐laden flow

Yang, Shu-Qing

doi:10.1029/2005jf000452

Cited by 21 publications

(36 citation statements)

References 39 publications

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“…Estimates of the turbulent velocity profile are required to quantify the amount of sediment transported in suspension [ Garcia , 2008]. Therefore, accurate characterization of the turbulent velocity profile through a physically based theory for prediction of turbulent flow interaction with suspended sediment is relevant for understanding sediment transport [ Smith and McLean , 1977; Gust and Southard , 1983; Villaret and Trowbridge , 1991; Yang , 2007; Garcia , 2008].…”

Section: Introductionmentioning

confidence: 99%

“…The log‐wake law contains two free adjustable parameters ( κ and Π), which means that the log‐wake results cannot add direct physical insight on the turbulent momentum transfer in sediment‐laden flows. The results of Valiani [1988] and Guo and Julien [2001], therefore, relied on an empirical analysis rather than on a theory for the turbulent momentum transfer [ Yang , 2007]. This unsolved issue is the basis of the present work.…”

Section: Introductionmentioning

confidence: 99%

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Is the von Kármán constant affected by sediment suspension?

Castro-Orgaz¹,

Giráldez²,

Mateos³

et al. 2012

J. Geophys. Res.

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[1] Is the von Kármán constant affected by sediment suspension? The presence of suspended sediment in channels and fluvial streams has been known for decades to affect turbulence transfer mechanism in sediment-laden flows, and, therefore, the transport and fate of sediments that determine the bathymetry of natural water courses. This study explores the density stratification effects on the turbulent velocity profile and its impact on the transport of sediment. There is as yet no consensus in the scientific community on the effect of sediment suspension on the von Kármán parameter, k. Two different theories based on the empirical log-wake velocity profile are currently under debate: One supports a universal value of k = 0.41 and a strength of the wake, P, that is affected by suspended sediment. The other suggests that both k and P could vary with suspended sediment. These different theories result in a conceptual problem regarding the effect of suspended sediment on k, which has divided the research area. In this study, a new mixing length theory is proposed to describe theoretically the turbulent velocity profile. The analytical approach provides added insight defining k as a turbulent parameter which varies with the distance to the bed in sediment-laden flows. The theory is compared with previous experimental data and simulations using a k-ɛ turbulence closure to the Reynolds averaged Navier Stokes equations model. The mixing length model indicates that the two contradictory theories incorporate the stratified flow effect into a different component of the log-wake law. The results of this work show that the log-wake fit with a reduced k is the physically coherent approximation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Is the von Kármán constant affected by sediment suspension?

Castro-Orgaz¹,

Giráldez²,

Mateos³

et al. 2012

J. Geophys. Res.

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“…Accurate characterization of vertical SSC profiles is imperative to quantify the SST rate (Mclean, 1991), which is crucial in morphodynamic studies whenever suspended load is dominant. Efforts are still being made using physics-based considerations of bulk sediment concentration (Mazumder and Ghoshal, 2006), vertical momentum flux (Yang, 2007), suspended sediment stratification (Villaret and Trowbridge, 1991;Herrmann and Madsen, 2007), and modified diffusion theory (Nielsen and Teakle, 2004;Chen et al, 2013) to obtain satisfactory simulation of SSC profiles even in steady and uniform sediment-laden flows under the state of dynamic equilibrium transport. However, under non-uniform or non-stationary conditions, the deviations of the vertical SSC profile from the local equilibrium state could be fairly large for fine sediments, because suspended sediment dynamics require a relatively large distance or time to approach equilibrium, that is, the saturation recovery process.…”

Section: Introductionmentioning

confidence: 99%

Challenges to the representation of suspended sediment transfer using a depth‐averaged flux

Chen

Huang

Liu

et al. 2016

Earth Surf Processes Landf

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The sediment saturation recovery process (i.e. the adaptation of suspended sediment concentration [SSC] to local forcing) is the main feature of the non‐equilibrium suspended sediment transport (SST) frequently occurring in fluvial, estuarine and coastal waters. In order to quantitatively describe this phenomenon, a series solution is analytically derived, including the evolution of both vertical SSC profile and near‐bed sediment flux (NBSF), and is verified by net erosion and net deposition experiments, respectively. The results suggest that the sediment saturation recovery process involves vertically varying fluxes that are not represented correctly by depth‐averaging. Consequently, a vertical two‐dimensional (2D) combined scheme is established and applied respectively in to a dredged trench and to a sand wave feature to demonstrate this argument. By analyzing the variations of the calculated depth‐averaged SSC and NBSF we reveal that the equilibrium state presented by the sediment carrying capacity (SCC) form of the NBSF, which is usually applied in depth‐integrated SST models, lags behind the actual dynamic bed equilibrium state. Moreover, the key factor α, the so‐called saturation recovery coefficient within this form, is not only a function of local Rouse number but also is influenced by the local SSC profile. Finally, a three‐dimensional (3D) non‐orthogonal curvilinear body‐fitted SST model is developed and validated in the Yangtze estuary, China, combined with the in situ hourly hydrographic data from August 14–15, 2007 during spring tide in the wet season. Model results confirm that the vertically varying sediment saturation recovery process, the discrepancies between the actual and SCC form of NBSF and non‐constant value of α are significant in actual real geomorphic cases. The quantitative morphological change resulting from variations in environmental conditions may not be correctly represented by uncorrected depth‐integrated SST models if they do not treat the effects of vertical motion on the sediment saturation recovery process. Copyright © 2016 John Wiley & Sons, Ltd.

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“…Yang (2002Yang ( , 2005 highlighted the importance of the momentum flux u v for the determination of velocity and Reynolds shear stress distribution, he pointed out that the direct consequence of the flux is that the streamwise velocity profile cannot be described by the universal log-law and the Reynolds shear stress does not follow the standard linear relationship. Yang et al (2004a) and Yang et al (2007) found that the wall-normal velocity caused by sediment settlement results in the reduction of von Karman constant in sediment-laden flows. Yang et al (2004b) revealed that the nonzero wall-normal velocity is responsible for the dip-phenomenon in a uniform channel flow.…”

Section: Introductionmentioning

confidence: 99%

Reynolds shear stress distributions in a gradually varied flow in a roughened channel

Yang

Lee

2007

Journal of Hydraulic Research

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The Reynolds shear stress distribution in non-uniform flows has been investigated. The theoretical results show that the wall-normal velocity causes the deviation of Reynolds shear stress from the standard linear distribution, i.e. −u v /u 2 * = 1 − y/ h, but the sum of Reynolds shear stress and the momentum flux, i.e. −(u v + u v)/u 2 * remains a linear distribution. By connecting the velocity gradient with Reynolds shear stress, the study demonstrates theoretically that the linear distribution of Reynolds shear stress and semi-logarithmic distribution of velocity (i.e., log-law) can be observed when and only when the wall-normal velocity is zero; the concave distribution of Reynolds shear stress and dip-phenomenon can be observed when and only when the wall-normal velocity is downward; the convex distribution of Reynolds shear stress can be observed and the wake-law correction is needed when and only when the upflow occurs. The theoretical results are in good agreement with experimental data. RÉSUMÉLa distribution du cisaillement de Reynolds dans des écoulements non uniformes a été étudiée. Les résultats théoriques montrent que la vitesse normale à la partoi produit une déviation du cisaillement de Reynolds par rapport à la distribution linéaire standard, i.e. −u v /u 2 * = 1 − y/ h, mais la somme du cisaillement de Reynolds et du débit de quantité de mouvement, i.e −(u v + u v)/u 2 * demeure une distribution linéaire. En reliant le gradient de vitesse au cisaillement de Reynolds, l'étude démontre que le phénomène de chute est provoqué par la vitesse normale à la paroi de haut en bas. Les résultats théoriques sont en bon accord avec des données expérimentales.

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Turbulent transfer mechanism in sediment‐laden flow

Cited by 21 publications

References 39 publications

Is the von Kármán constant affected by sediment suspension?

Is the von Kármán constant affected by sediment suspension?

Challenges to the representation of suspended sediment transfer using a depth‐averaged flux

Reynolds shear stress distributions in a gradually varied flow in a roughened channel

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