Role of Bed Discordance at Asymmetrical River Confluences

Bradbrook, K. F.; Lane, Stuart N.; Richards, Keith; Biron, Pascale M.; Roy, Alain

doi:10.1061/(asce)0733-9429(2001)127:5(351)

Cited by 169 publications

(123 citation statements)

References 38 publications

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“…Section A is close to the confluence zone, showing higher downstream velocity within the true left channel and an area of lower velocity flow in a stagnation zone between the two flows. The vectors show no real pattern of secondary flow, with no helical circulation apparent, as has been reported from smaller channel confluences (see, e.g., Ashmore et al, 1992;Rhoads and Kenworthy, 1998), some laboratory experiments (see, e.g., Mosley, 1976) and numerical simulations (see, e.g., Bradbrook et al, 2000Bradbrook et al, , 2001. Similarly, there appears to be no clear influence of bed discordance on secondary flow generation through this zone.…”

Section: Secondary Circulationmentioning

confidence: 48%

“…Research investigating the processes of flow at river channel confluences has highlighted the possible importance of secondary flows and their controls on channel geometry, channel dynamics, sediment transport and flow mixing (e.g. Ashmore et al, 1992;Best, 1986Best, , 1987Best, , 1988Best and Reid, 1984;Best and Roy, 1991;Biron et al, 1993Biron et al, , 1996Bradbrook et al, 1998Bradbrook et al, , 2000Bradbrook et al, , 2001Lane et al, 2000;McLelland et al, 1999;Mosley, 1976;Rhoads and Kenworthy, 1998;Rhoads and Sukhodolov, 2001). The classical model of flow at a confluence involves divergence between near-bed and nearsurface flows as a result of the interaction between pressure gradient forcing and bed topographic steering.…”

Section: Introductionmentioning

confidence: 99%

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Form roughness and the absence of secondary flow in a large confluence–diffluence, Rio Paraná, Argentina

Parsons

Best

Lane

et al. 2006

Earth Surf Processes Landf

161

133

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Confluence-diffluence units are key elements within many river networks, having a major impact upon the routing of flow and sediment, and hence upon channel change. Although much progress has been made in understanding river confluences, and increasing attention is being paid to bifurcations and the important role of bifurcation asymmetry, most studies have been conducted in laboratory flumes or within small rivers with width:depth (aspect) ratios less than 50. This paper presents results of a field-based study that details the bed morphology and 3D flow structure within a very large confluence-diffluence in the Río Paraná, Argentina, with a width:depth ratio of approximately 200. Flow within the confluence-diffluence is dominated largely by the bed roughness, in the form of sand dunes; coherent, channel-scale, secondary flow cells, that have been identified as important aspects of the flow field within smaller channels, and assumed to be present within large rivers, are generally absent in this reach. This finding has profound implications for flow mixing rates, sediment transport rates and pathways, and thus the interpretation of confluence-diffluence morphology and sedimentology.

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Section: Secondary Circulationmentioning

confidence: 48%

Section: Introductionmentioning

confidence: 99%

Form roughness and the absence of secondary flow in a large confluence–diffluence, Rio Paraná, Argentina

Parsons

Best

Lane

et al. 2006

Earth Surf Processes Landf

161

133

View full text Add to dashboard Cite

show abstract

“…In particular, most of the CFD simulations have been conducted using the Reynolds Averaged Navier-Stokes (RANS) equations or Large Eddy Simulation (LES) models. For instance, the data of Biron et al [3] were taken into account for the simulations of Bradbrook et al [28] and Biron et al [10]. Shakibainia et al [29] used SSIIM 2.0, a RANS-based turbulent model, to reproduce the experiments of Shumate [18].…”

Section: Introductionmentioning

confidence: 99%

Effect of the Junction Angle on Turbulent Flow at a Hydraulic Confluence

Penna

Marchis

Canelas

et al. 2018

Water

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Despite the existing knowledge concerning the hydrodynamic processes at river junctions, there is still a lack of information regarding the particular case of low width and discharge ratios, which are the typical conditions of mountain river confluences. Aiming at filling this gap, laboratory and numerical experiments were conducted, comparing the results with literature findings. Ten different confluences from 45 • to 90 • were simulated to study the effects of the junction angle on the flow structure, using a numerical code that solves the 3D Reynolds Averaged Navier-Stokes (RANS) equations with the k-turbulence closure model. The results showed that the higher the junction angle, the wider and longer the retardation zone at the upstream junction corner and the separation zone, and the greater the flow deflection at the entrance of the tributary into the post-confluence channel. Furthermore, it was shown that the maximum streamwise velocity does not necessarily increase with the junction angle and that it is not always located in the contraction section.

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“…The software uses the finite volume approach to solve the fully 3D form of the Reynolds Averaged NavierStokes (RANS) equations in each cell of the modelling domain. The model is described in detail elsewhere (Bradbrook et al [14,15]) and has been used extensively in both laboratory Haltigin et al [16,17] and field studies (Ferguson et al [18]; Carré et al [13]). The bed topography survey was used to create an "object-bed" (Haltigin et al [16]).…”

Section: Methodsmentioning

confidence: 99%

Hydraulics of stream deflectors used in fish-habitat restoration schemes

Biron¹,

Carré²,

Gaskin³

2009

WIT Transactions on Ecology and the Environment

Self Cite

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Despite the widespread use of in-stream structures in stream restoration projects to enhance the quality of physical habitat, it is only recently that the hydraulics of these structures have been studied in detail, typically using simplistic geometries in laboratory experiments. The objective of this study is to examine hydraulics around complex flow deflectors using a combination of laboratory, field and three-dimensional (3D) Computational Fluid Dynamics (CFD) approaches. In the laboratory, Acoustic Doppler Velocimeter (ADV) measurements revealed that flow overtopping the structure modifies the scour zone and bed shear stress pattern compared to a greater structure height. In the field, a 3D CFD model, which was calibrated at low flow using ADV and Particle Image Velocimetry measurements, was used to investigate both low and high flow (overtopping) conditions. A complex 3D pattern in the recirculation zones downstream of the deflectors is observed in the overtopping simulations, highlighting the limits of habitat structure studies based on depth-averaged (2D) models. The comparison with laboratory data is complicated by the fact that a dug pool was used in the field, which does not correspond to the position of the pools that developed near deflectors over a mobile bed in the laboratory. As natural rivers exhibit a wide range of discharges with various overtopping ratios, it is essential to pursue work using 3D CFD to test how different deflector height, length and angle designs affect the position and dimension of scour zones and the long-term viability of fish-habitat restoration projects.

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Role of Bed Discordance at Asymmetrical River Confluences

Cited by 169 publications

References 38 publications

Form roughness and the absence of secondary flow in a large confluence–diffluence, Rio Paraná, Argentina

Form roughness and the absence of secondary flow in a large confluence–diffluence, Rio Paraná, Argentina

Effect of the Junction Angle on Turbulent Flow at a Hydraulic Confluence

Hydraulics of stream deflectors used in fish-habitat restoration schemes

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