Numerical simulation of a weak breaking tidal bore

Lubin, Pierre; Glockner, Stéphane; Chanson, Hubert

doi:10.1016/j.mechrescom.2009.09.008

Cited by 40 publications

(17 citation statements)

References 11 publications

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“…Over the last decade, the hydraulic behaviors of tidal bores have been extensively investigated through field observations [4][5][6], flume experiments [7,8], and numerical modeling [9][10][11]. It is generally accepted that undular bores begin to form with a Froude (F r ) number slightly above 1.…”

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confidence: 99%

Sedimentation processes and sedimentary characteristics of tidal bores along the north bank of the Qiantang Estuary

et al. 2012

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A tidal bore is a unique Earth surface process, characterized by its highly destructive energy, predictable periodicities and magnitudes, and the production of characteristic sedimentary features. Tidal bores and associated rapid flood flows are highly turbulent flows of the upper-flow regime with a velocity over several meters per second. Reynolds (R e ) and Froude (F r ) numbers, respectively, are larger than 10 4 and 1.0, making them significantly different from regular tidal flows but analogous to turbidity currents. Until now, understanding of tidal-bore depositional processes and products has been limited because of the difficulty and hazards involved with gauging tidal bores directly. The Qiantang bore is known as the largest breaking bore in the world. Field surveys were carried out in May 2010, along the north bank of the Qiantang Estuary to observe the occurrence of peak bores, including regular observations of current, water level and turbidity at the main channel. Several short cores were sampled on the intertidal flats to study the characteristic sedimentary features of tidal bores. Hydrodynamic and sedimentological studies show that the processes of sediment resuspension, transport and deposition are controlled primarily by the tidal bores, and the subsequent abruptly accelerated and decelerated flood flows, which only account for one tenth of each semidiurnal tidal cycle in the estuary. Tidal-bore deposits are generally poorly sorted because of rapid sedimentation after highly mixed suspension by intense turbulence. This behavior is characteristic of the absence of tractive-current depositional components in a C-M diagram. It also goes along with well-developed massive bedding, graded bedding, basal erosion structures, convolute bedding and dewatering structures. Together, these sedimentary features can constitute fingerprinting of turbidites, widely distributed in the deep-water environment. However, a tidal bore is triggered by intensely deformed tidal waves propagating into a shallow-water environment, which returns to regular tidal flows rapidly after the passage of the bore head. The tidal-bore deposits are usually bounded by the intertidal-flat deposits with typical tidal beddings at the top and on both flanks. The difference between tidal-bore deposits (TBD) and tidal sandy/muddy deposits (TSD/TMD) is evident not only in sedimentary structures, but also in the grain-size composition. They can be clearly distinguished in grain-size bivariate plots, typically the plot of mean grain size vs. standard deviation (or sorting). Some trend variations generally exist in mean grain size with TBD>TSD>TMD, sorting with TMD>TBD>TSD (larger value indicating poorer sorting), and both skewness and kurtosis with TSD>TBD>TMD. These findings will undoubtedly shed new light on our understanding of tidal-bore sedimentology, ancient tidal-bore sedimentary facies and environments, and related oil-and-gas field prospecting.

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confidence: 99%

Sedimentation processes and sedimentary characteristics of tidal bores along the north bank of the Qiantang Estuary

et al. 2012

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“…These were best seen by some sudden and rapid fluctuations of the transverse and vertical velocity data (Fig. 5), while some recent numerical modelling highlighted the production of large turbulent eddies beneath the bore front and their upstream advection behind the bore [24,40]. These vortical structures remained next to the bed as the bore propagated upstream and the presence of these persisting turbulent structures indicated that a great amount of sediment matters was placed in suspension and advected upstream.…”

Section: Turbulent Flow Fieldmentioning

confidence: 83%

Current knowledge in tidal bores and their environmental, ecological and cultural impacts

Chanson

2009

Environ Fluid Mech

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A tidal bore is a series of waves propagating upstream as the tidal flow turns to rising. It forms during the spring tide conditions when the tidal range exceeds 5-6 m and the flood tide is confined to a narrow funnelled estuary with low freshwater levels. A tidal bore is associated with a massive mixing of the estuarine waters that stirs the organic matter and creates some rich fishing grounds. Its occurrence is essential to many ecological processes and the survival of unique eco-systems. The tidal bore is also an integral part of the cultural heritage in many regions: the Qiantang River bore in China, the Severn River bore in UK, the Dordogne River in France. In this contribution, the environmental, ecological and cultural impacts of tidal bores are reviewed, explained and discussed.

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“…The turbulent viscosity μ T is calculated with the Mixed Scale model (Sagaut 1998), which has proved its accuracy for geophysical flows (Lubin 2004;Helluy et al 2005;Lubin et al 2006b, Lubin et al 2010a-2010b. Based on the review of Lubin and Caltagirone (2010), we find that the most widely used subgrid scale model is the Smagorinsky model.…”

Section: Governing Equationsmentioning

confidence: 99%

Numerical Simulations of Spilling Breaking Waves

Lubin

Glockner

Kimmoun

et al. 2011

Int. Conf. Coastal. Eng.

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Numerical simulation of spilling breaking waves is still a very challenging aim to achieve since small interface deformations, air entrainment and vorticity generation are involved during the early stage of the breaking of the wave. High mesh grid resolutions and appropriate numerical methods are required to capture accurately the length scales of the complex mechanisms responsible for the start of the breaking (small plunging jet, white foam, etc.). Numerical works usually showed better agreements when simulating plunging breaking waves than the spilling case compared with available experimental data. Kimmoun and Branger (2007) recently experimented surf-zone breaking waves. Detailed pictures showed a short spilling event occurred at the crest of the waves, before degenerating into strong plunging breaker. This work is devoted to the qualitative comparison of our numerical results with the experimental observations, as we will focus on capturing and describing the spilling phase experimented.

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Numerical simulation of a weak breaking tidal bore

Cited by 40 publications

References 11 publications

Sedimentation processes and sedimentary characteristics of tidal bores along the north bank of the Qiantang Estuary

Sedimentation processes and sedimentary characteristics of tidal bores along the north bank of the Qiantang Estuary

Current knowledge in tidal bores and their environmental, ecological and cultural impacts

Numerical Simulations of Spilling Breaking Waves

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