Water flow and sediment transport at open-channel confluences: an experimental study

Yuan, Saiyu; Tang, Hongwu; Xiao, Yang; Qiu, Xuehan; Xia, Yang

doi:10.1080/00221686.2017.1354932

Cited by 83 publications

(62 citation statements)

References 39 publications

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“…Exposure of the bar at low flow stage enhances the steering effect, forcing flow toward the right bank of the CS and contributing to the development of jet‐like flow within the confluence. Though documented in some laboratory (Schindfessel et al, ; Yuan et al, ) and discordant confluences (Guillén Ludeña et al, ; Sukhodolov et al, ), jet‐like flow at concordant confluences is a departure from the standard conceptual model of asymmetrical confluences (Rhoads, ). At SALINE, flow separation was caused mainly by the local protrusion of the bank near the downstream junction corner of the SD along with retreat of the channel bank associated with channel widening downstream from the protrusion.…”

Section: Discussionmentioning

confidence: 99%

LSPIV Measurements of Two‐Dimensional Flow Structure in Streams Using Small Unmanned Aerial Systems: 2. Hydrodynamic Mapping at River Confluences

Lewis

Rhoads

2018

Water Resources Research

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Although past field work at stream confluences has relied on velocity information at specific cross sections to examine flow structure, detailed characterizations of spatial and temporal variations in the hydrodynamics of confluences are lacking. This study uses large‐scale particle image velocimetry (LSPIV) obtained from small unmanned aerial systems (sUAS), a method evaluated in a companion paper, to map surficial patterns of mean flow and turbulent structures at two small stream confluences in unprecedented levels of detail. LSPIV reveals two‐dimensional flow patterns within different hydrodynamic zones in each confluence as well as similarities and differences in hydrodynamic conditions between the confluences. As expected based on extant conceptual models of confluence hydrodynamics, the spatial arrangement of characteristic hydrodynamic zones varies with confluence planform geometry and with changes in incoming flow conditions. However, local morphological features, such as bars and irregularities in channel banks, also exert a strong influence on the spatial structure of flow and in some cases influence confluence hydrodynamics to an extent comparable to changes in incoming flow conditions. The usefulness of sUAS‐based LSPIV is demonstrated by the correspondence between patterns of flow curvature revealed by this method and patterns of helical motion documented at cross sections within the confluences using acoustic Doppler velocimetry. The method can also be used to characterize the structure of turbulent vortices within the mixing interface between confluent streams under appropriate conditions. Hydrodynamic mapping using sUAS‐based LSPIV enriches the interpretation of traditional in‐stream velocity data acquired in the field and provides information on surface velocity patterns in rivers at a resolution similar to that of numerical models.

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Section: Discussionmentioning

confidence: 99%

LSPIV Measurements of Two‐Dimensional Flow Structure in Streams Using Small Unmanned Aerial Systems: 2. Hydrodynamic Mapping at River Confluences

Lewis

Rhoads

2018

Water Resources Research

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“…According to the previous studies, a depositional sediment bar is formed as a result of the reduced pressure and secondary circulations at the separation zone close to the inner wall of the post‐confluence channel (Nazari‐Giglou et al, ; Shakibainia, Majdzadeh‐Tabatabai, & Zarrati, ; Yuan et al, ). Biron, Richer, Kirkbride, Roy, and Han () reported that greater values of lateral flow and densimetric Froude number lead to a farther distance of sediment bar from the beginning of post‐confluence channel, that is, higher N values.…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, increasing the vane angle and pier diameter leads to more scouring. In another experimental study, Yuan, Tang, Xiao, Qiu, and Xia () investigated the effect of increasing the lateral discharge to a junction with 90° confluence angle and observed that the location of maximum scour depth moves downstream in parallel to the main channel wall. Amini, Balouchi, and Shafai‐Bajestan () studied the effect of collars on reducing the scour depth in a channel confluence.…”

Section: Introductionmentioning

confidence: 99%

Effect of side slope of main channels on formation and penetration of scour hole in confluences

Khosravinia

Nikpour

Malekpour

et al. 2019

River Research & Apps

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In an open‐channel confluence, deep scour holes and depositional point bars are usually formed due to high bed‐shear stresses and secondary circulations. In the present study, presuming the effectiveness of channel geometry on the flow dynamics at the confluence, some variables including different side slope angles of the main channel (θ = 45°, 60°, 75°, 90°), lateral to downstream discharge ratio (Qr), and downstream densimetric Froude number (Frg3) were experimentally studied under clear‐water condition for the confluence angle α = 90°. According to the results, the increase of θ led to a greater penetration of scour hole across the main and tributary channels, whereas a little scour development was observed along those channels. Meanwhile, an increase in Qr and Frg3 caused further scouring, but their effects on the dimensions of scour hole diminished with increase of θ. Thus, with increase of Qr from 0.194 to 0.552, the mean penetration rate of scour hole to all directions for θ = 45°, 60°, 75°, and 90° was obtained 42.8%, 32.4%, 25%, and 20.5%, respectively. In addition, considering the effect of θ, Qr, and Frg3, some empirical relationships were obtained for estimating the penetration length of scour hole. The derived relationships show that Frg3 plays more important role on the dimensions of scour hole than θ.

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“…Despite extensive investigation of hydrodynamics, morphodynamics, and mixing at river confluences in the last decades using field, laboratory and numerical methods [18][19][20], only two studies have focused on HEF in river confluences so far. Song et al [21] and Cheng et al [22] studied HEF about a river confluence, looking at the influence of hydraulic conductivity and river morphology on vertical hyporheic fluxes (VHF), which were investigated through a one-dimensional steady-state heat model, using temperature time series with resistance temperature detectors.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Hyporheic Exchange Drivers and Patterns within a Low-Gradient, First-Order, River Confluence during Low and High Flow

Martone

Gualtieri

Endreny

2020

Water

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Confluences are nodes in riverine networks characterized by complex three-dimensional changes in flow hydrodynamics and riverbed morphology, and are valued for important ecological functions. This physical complexity is often investigated within the water column or riverbed, while few studies have focused on hyporheic fluxes, which is the mixing of surface water and groundwater across the riverbed. This study aims to understand how hyporheic flux across the riverbed is organized by confluence physical drivers. Field investigations were carried out at a low gradient, headwater confluence between Baltimore Brook and Cold Brook in Marcellus, New York, USA. The study measured channel bathymetry, hydraulic permeability, and vertical temperature profiles, as indicators of the hyporheic exchange due to temperature gradients. Confluence geometry, hydrodynamics, and morphodynamics were found to significantly affect hyporheic exchange rate and patterns. Local scale bed morphology, such as the confluence scour hole and minor topographic irregularities, influenced the distribution of bed pressure head and the related patterns of downwelling/upwelling. Furthermore, classical back-to-back bend planform and the related secondary circulation probably affected hyporheic exchange patterns around the confluence shear layer. Finally, even variations in the hydrological conditions played a role on hyporheic fluxes modifying confluence planform, and, in turn, flow circulation patterns.

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Water flow and sediment transport at open-channel confluences: an experimental study

Cited by 83 publications

References 39 publications

LSPIV Measurements of Two‐Dimensional Flow Structure in Streams Using Small Unmanned Aerial Systems: 2. Hydrodynamic Mapping at River Confluences

LSPIV Measurements of Two‐Dimensional Flow Structure in Streams Using Small Unmanned Aerial Systems: 2. Hydrodynamic Mapping at River Confluences

Effect of side slope of main channels on formation and penetration of scour hole in confluences

Characterization of Hyporheic Exchange Drivers and Patterns within a Low-Gradient, First-Order, River Confluence during Low and High Flow

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