Effects of Bed Discordance on Flow Dynamics at Open Channel Confluences

Biron, Pascale M.; Best, James L.; Roy, Alain

doi:10.1061/(asce)0733-9429(1996)122:12(676)

Cited by 206 publications

(174 citation statements)

References 22 publications

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“…The effects of bed height discordance on the flow pattern of the confluence zone were studied by Biron et al (1996), Best and Roy (1991). Biron et al (1996) used two-component Laser Doppler Anemometer (LDA) to measure streamwise, u, and vertical, w, velocities in a confluence model with a 30 junction angle, at 82 vertical profiles along 11 cross-sections, each profile having only 5 measuring points.…”

Section: Introductionmentioning

confidence: 99%

“…Biron et al (1996) used two-component Laser Doppler Anemometer (LDA) to measure streamwise, u, and vertical, w, velocities in a confluence model with a 30 junction angle, at 82 vertical profiles along 11 cross-sections, each profile having only 5 measuring points. It is worth mentioning that the aspect ratio (channel width/ flow depth) applied in the study was very low, namely 0.5 and 0.75 in the tributary and main channel and 0.94 in the post confluence channel.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, bed discordance was found to modify the mainstream flow deflection at the bed and to create important near-bed and water surface level differences at the downstream junction corner. However, Biron et al (1996) admit that further laboratory studies are required for higher junction angles, mobile bed, higher width/depth ratios, and three-component velocity measurements (u, v, w) in order to assess the influence of bed discordance and bed morphology on the flow dynamics of channel confluences.…”

Section: Introductionmentioning

confidence: 99%

“…The complete data set will also be used for the validation of 3D computational fluid dynamics codes. Table 1 shows a comparison of three experimental studies at fixed bed open channel confluences for concordant and discordant beds conducted by Biron et al (1996), Weber et al (2001) and the one described in the present study.…”

Section: Introductionmentioning

confidence: 99%

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Three dimensional flow field at confluent fixed-bed open channels

Birjukova¹,

Ludeña²,

Alegria³

et al. 2014

River Flow 2014

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River confluences are known for their marked 3D patterns and, due to the complexity of local flow features and bed morphology, they require particular consideration. Although there are studies on the flow structure in junctions of two streams, amore detailed description of the flow patterns is still required. The objective of this work is to contribute to such description at river confluence for concordant bed, where both main and tributary channel beds have the same elevation. For that purpose, a set of experiments with fixed bed under quasi-uniform approach flow conditions was carried out. The experimental facility included a 12 m long and 1 m wide main channel, and a 4.5 m long and 0.15 m wide tributary channel. The confluence angle was 70° so as to represent common natural conditions and the discharge ratio between discharges in the tributary and in the main channel was kept constant. An Acoustic Doppler Velocimeter (ADV) with a side-looking configuration was used to measure the three components of flow velocity on a dense grid of measuring points, providing the accurate characterization of the mean flow and second-order velocity moments. The acquired data set constitutes the most refined characterization of river confluence flow structures known to date, due to the adopted temporal and spatial discretization, and may serve for the validation of 3D numerical models of complex confluent flows. Flow dynamics zones typical of confluent beds are present in the studied case. The separation zone limits the effective lateral flow cross-section, and, hence, results in the added acceleration of the mainstream flow near the downstream junction corner. The upward orientated vertical velocities of high magnitude were observed all along the separation zone.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Three dimensional flow field at confluent fixed-bed open channels

Birjukova¹,

Ludeña²,

Alegria³

et al. 2014

River Flow 2014

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show abstract

“…The non-dimensional length and width of the separation zone seem to be of the order of magnitude of that observed by Biron et al (1996) [5], indicating that the main channel aspect ratio may not influence the relative size of the stagnation zone. This conclusion requires future confirmation.…”

Section: Literature Reviewmentioning

confidence: 68%

Study of Flow Field of River for Hydro Kinetic Turbine Installation

2015

International Conference on Advancements and Recent Innovations in Mechanical, Production and Industrial Engineering

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An optimized location finding in river, for efficient power generation through hydrokinetic turbine, is very important. Power generation through hydrokinetic turbine is mainly depend upon the flow velocity of the river and also flow features and channel morphology which greatly influence the installation of hydrokinetic turbine. In the present work, the flow field of river has been studied through the fluent software to identify the optimum location for the installation of hydrokinetic turbine. The discharge data of a selected river has been analyzed and discussed. It also has been investigated the effect of flow field on the power generation from hydrokinetic turbine.

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Time-averaged flow structure in the central region of a stream confluence

Rhoads

Kenworthy

1998

Earth Surf. Process. Landforms

162

173

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Previous process-oriented field studies of stream confluences have focused mainly on fluvial dynamics at or immediately downstream of the location where the confluent flows enter the downstream channel. This study examines in detail the spatial evolution of the time-averaged downstream velocity, cross-stream velocity, and temperature fields between the junction apex, where the flows initially meet, and the entrance to the downstream channel. A well-defined, vertically oriented mixing interface exists within this portion of the confluence, suggesting that lateral mixing of the incoming flows is limited. The downstream velocity field near the junction apex is characterized by two high-velocity cores separated by an intervening region of low-velocity or recirculating fluid. In the downstream direction, the high-velocity cores move inwards towards the mixing interface and high-velocity fluid progressively extends downwards into a zone of scour, resulting in an increase in flow velocity in the centre of the confluence. The cross-stream velocity field is dominated by flow convergence, but also includes a component associated with a consistent pattern of secondary circulation. This pattern is characterized by two surface-convergent helical cells, one on each side of the mixing interface. The helical cells appear to be the mechanism by which high-momentum fluid near the surface is advected downwards into the zone of scour. For transport-ineffective flows, the dimensions and intensities of the cells are controlled by the momentum ratio of the confluent streams and by the extant bed morphology within the confluence. Although the flow structure of formative events was not measured directly in this study, documented patterns of erosion and deposition within the central region of the confluence suggest that these events are dynamically similar to the measured flows, except for the fact that formative flows are not constrained by, but can reshape, the bed morphology. The results of this investigation are consistent with and augment previous findings on time-averaged flow structure in the downstream portion of the confluence.

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Effects of Bed Discordance on Flow Dynamics at Open Channel Confluences

Cited by 206 publications

References 22 publications

Three dimensional flow field at confluent fixed-bed open channels

Three dimensional flow field at confluent fixed-bed open channels

Study of Flow Field of River for Hydro Kinetic Turbine Installation

Time-averaged flow structure in the central region of a stream confluence

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