Cyclonic Spirals in Tidally Accelerating Bottom Boundary Layers in the Zhujiang (Pearl River) Estuary

Wu, Jiaxue; Liu, Huan; Ren, Jie; Deng, Junjie

doi:10.1175/2011jpo4565.1

Cited by 13 publications

(6 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, by applying the calculated Kolmogorov constants using the SFM applied to vertical velocity components, we estimate that the dissipation calculation by Wu et al . [] at 5.9 cm above the bed (25≤ y + ≤ 200 and 0.0424

\leq u_{τ} \leq

0.339 cms −1 ) in the Pearl River Estuary, could be improved by 45–90% and the dissipation in Lorke [], at 12 cm above the bed (82≤ y + ≤ 312 and 0.0683

\leq u_{τ} \leq

0.26 cms −1 ) in Lake Constance, could be improved by 40–65%. Therefore, using our values for the Kolmogorov 2/3 constants, that account for the anisotropy of the flow, can result in considerably more accurate calculation of the rate of dissipation in geophysical boundary layers.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of the structure function method to compute turbulent dissipation within boundary layers using numerical simulations

2016

View full text Add to dashboard Cite

Well-resolved numerical simulations of turbulent open channel flows are analyzed to evaluate the accuracy of the 2nd order structure function method (SFM) in estimating the rate of dissipation of turbulent kinetic energy within boundary layers. The objective is to assess the variation in the 2/3 Kolmogorov constants due to flow anisotropy with distance from the wall. Comparison of the dissipation calculated directly from the numerical data, with that from the SFM shows that usage of the canonical constants, based on the assumption of local isotropy, can result in considerable error (>50%) in the prediction of dissipation when using the vertical or spanwise velocity components. From the numerically calculated dissipation, optimal Kolmogorov 2/3 constants were obtained and empirical relations, which account for near-wall effects, were proposed. Usage of the optimal constants will improve estimation of the dissipation rate when the SFM is applied to compute dissipation in geophysical boundary-layer flows.

show abstract

\leq u_{τ} \leq

0.339 cms −1 ) in the Pearl River Estuary, could be improved by 45–90% and the dissipation in Lorke [], at 12 cm above the bed (82≤ y + ≤ 312 and 0.0683

\leq u_{τ} \leq

Section: Discussionmentioning

confidence: 99%

Evaluation of the structure function method to compute turbulent dissipation within boundary layers using numerical simulations

2016

View full text Add to dashboard Cite

show abstract

“…[27], which is used to describe DBL thickness in systems where turbulence controls this thickness [18]. It is interesting that the variation of BBL thickness follows the speed [23,24,28], contrary to the DBL finding. The variation of diffusion flux may be interpreted by two mechanisms, which are responses to the change of water overlying the sediment and the turbulent intensity.…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, the relationship between the turbulent energy dissipation rate and mean velocity is not strong. This indicates that the turbulence is caused not only by shear of the mean velocity, but also probably by surface waves, local topography, sediment transport and buoyant flux [23][24][25]. Estimating the production of turbulence is limited by the data, and thus will not be discussed further.…”

Section: Numerical Model Profilementioning

confidence: 99%

Variable diffusion boundary layer and diffusion flux at sediment-water interface in response to dynamic forcing over an intertidal mudflat

2012

View full text Add to dashboard Cite

The diffusion boundary layer (DBL) significantly limits the exchange between sediment and overlying water and therefore becomes a bottleneck of diffusive vertical flux at the sediment-water interface (SWI). Variable DBL thickness and diffusion flux in response to dynamic forcing may influence replenishment of nutrients and secondary pollution in coastal waters. In situ measurements of velocity in the bottom boundary layer (BBL) and oxygen concentration in the DBL were made over an intertidal mudflat, using an acoustic Doppler current and mini profiler. A linear distributed zone in the oxygen profile, the profile slope discontinuity and variance of concentration can be used to derive accurate DBL thickness. Diffusion fluxes calculated from the water column and sediment are identical, and their bias is less than 6%. A numerical model PROFILE is used to simulate the in situ dissolved oxygen profile, and layered dissolved oxygen consumption rates in the sediment are calculated. The DBL thickness (0.10-0.35 mm) and diffusion flux (15.4-53.6 mmol m) vary with a factor of 3.5 during a tidal period. Over an intertidal mudflat, DBL thickness is controlled by flow speed U in the BBL, according to δ DBL =1686.1DU −1 +0.1 (D is the molecular diffusion coefficient).That is, the DBL thickness δ DBL increases with decreasing flow speed U. Changes of diffusion flux at the SWI are caused by variations in the water above the sediment and the turbulent mixing intensity. The diffusion flux is positively related to the turbulent dissipation rate, friction velocity and turbulent energy. Under the influence of dynamics in the BBL, DBL thickness and flux vary significantly. diffusion boundary layer, diffusion flux, dynamic forcing, mini profiler, dissolved oxygen, intertidal mudflat Citation:Wang J N, Zhao L, Wei H. Variable diffusion boundary layer and diffusion flux at sediment-water interface in response to dynamic forcing over an intertidal mudflat. Chin Sci Bull, 2012Bull, , 57: 15681577, doi: 10.1007 The diffusion boundary layer (DBL) is a thin (less than 1 mm) film of water covering the sediment. When solutes and particles are transported from the bottom boundary layer (BBL) to the DBL, molecular diffusion instead of turbulent eddy diffusion dominates the vertical transport [1][2][3]. The DBL limits exchange between the sediment and overlying water, and therefore becomes a bottleneck of diffusive vertical flux at the sediment-water interface (SWI). theoretically revealed that dynamic forcing in the BBL has a direct effect on DBL thickness and diffusion flux at the SWI. Under the influence of dynamics in the BBL, DBL thickness and flux vary significantly. Understanding how the DBL and diffusion transport responds to dynamic forcing is therefore crucial for accurately quantifying diffusion flux, and for estimating the replenishment of nutrients and secondary pollution in coastal waters. Modeling also requires numerical parameterization of diffusion flux as a function of BBL dynamics. The diffusive vertical flux of dissolved oxy...

show abstract

“…Two horizontal Reynolds stresses are defined as

τ_{x} = - ρ \overset{true¯}{u' w'}

and

τ_{y} = - ρ \overset{true¯}{v' w'}

, respectively, where the overbar denotes a temporal average. Since the pitch and roll angles of the ADV sensors on the tripod were both smaller than 3°, the eddy‐correlation method can give a reliable estimation of the Reynolds stresses and avoid the bias induced by the tilt of the ADV sensor (Kim et al, ; Wu et al, ).…”

Section: Methodsmentioning

confidence: 99%

Sediment Suspension by Straining‐Induced Convection at the Head of Salinity Intrusion

Zhang

2018

JGR Oceans

Self Cite

View full text Add to dashboard Cite

The tidal straining can generate convective motions and exert a periodic modification of turbulence and sediment transport in estuarine and coastal bottom boundary layers. However, the evidence and physics of convection and sediment suspension induced by tidal straining have not been straightforward. To examine these questions, mooring and transect surveys have been conducted in September 2015 in the region of the Yangtze River plume influence. Field observations and scaling analyses indicate an occurrence of convective motions at the head of saline wedge. Theoretical analyses of stratification evolution in the saline wedge show that unstable stratification and resultant convection are induced by tidal straining. Vertical turbulent velocity and eddy viscosity at the head of saline wedge are both larger than their neutral counterparts in the main body, largely enhancing sediment suspension at the head of saline wedge. Moreover, sediment suspension in both neutral and convection‐affected flows is supported by the variance of vertical turbulent velocity, rather than the shearing stress. Finally, the stability correction functions in the Monin‐Obukhov similarity theory can be simply derived from the local turbulent kinetic energy balance to successfully describe the effects of tidal straining on turbulent length scale, eddy viscosity, and sediment diffusivity in the convection‐affected flow. These recognitions may provide novel understanding of estuarine turbidity maxima, and the dynamical structure and processes for coastal hypoxia.

show abstract

Cyclonic Spirals in Tidally Accelerating Bottom Boundary Layers in the Zhujiang (Pearl River) Estuary

Cited by 13 publications

References 33 publications

Evaluation of the structure function method to compute turbulent dissipation within boundary layers using numerical simulations

Evaluation of the structure function method to compute turbulent dissipation within boundary layers using numerical simulations

Variable diffusion boundary layer and diffusion flux at sediment-water interface in response to dynamic forcing over an intertidal mudflat

Sediment Suspension by Straining‐Induced Convection at the Head of Salinity Intrusion

Contact Info

Product

Resources

About