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Braid bar

About: Braid bar is a research topic. Over the lifetime, 44 publications have been published within this topic receiving 3964 citations.

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TL;DR: In this paper, a physical model of a typical multi-anabranch river with three braid bars was established to explore the pollutant mixing characteristics in different branches, and the longitudinal velocities and pollutant concentrations in the seven branches were measured.
Abstract: A multi-anabranch river with three braid bars is a typical river pattern in nature, but no studies have been conducted to describe mixing characteristics of pollutants in the river. In this study, a physical model of a typical multi-anabranch river with three braid bars was established to explore the pollutant mixing characteristics in different branches. The multi-anabranch reach was separated into seven branches, B1, B2, B3, B4, B5, B6, and B7, by three braid bars. Five tracer release positions located 2.9 m upstream from the inlet section of the multi-anabranch reach were adopted, and the distances from the five positions to the left bank of the upstream main channel were 1/6B, 1/3B, 1/2B, 2/3B, and 5/6B(B is the width of the upstream main channel), respectively. The longitudinal velocities and pollutant concentrations in the seven branches were measured. The planar flow field and mixing characteristics of pollutants from the bottom to the surface in the multi-anabranch river were obtained and analyzed. The results show that the pollutant release positions are the main influencing factors in the pollutant transport process, and the diversion points and pollutant release positions jointly influence the percentage ratios of the pollutant fluxes in branches B1, B2, and B3 to the pollutant flux in the upstream main channel.

3 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the quadrant method to analyze the turbulence characteristics of flow around the island in a braided river model using 2-D bursting events technique, and they measured three velocity fluctuation components (u′, v′, w′) with Acoustic Doppler Velocimetry.
Abstract: Turbulent flow is a flow regime which is described by the anarchic property changes. This includes the rapid variation of pressure, high momentum convection and flow velocity in time and space. A turbulent phenomenon in a braided river is much more complex as compared to the straight and meandering rivers. Turbulent flow characteristics around the braid bar are not thoroughly studied till now. In the current paper, the quadrant method is used to analyze the turbulence characteristics of flow around the island in a braided river model using 2-D burstingevents technique. Three velocity fluctuation components (u′, v′, w′), were measured with Acoustic Doppler Velocimetry. Although many advances have been made within recent years in interpreting the mechanics of flow, transport of sediment and sedimentary architecture of braided rivers, many key issues remains to be addressed, in particular, the underlying processes of braid bar initiation. An attempt has been made herein to relate the depositional characteristics around the island in the braided river model to the sweep and ejection events. The concept of the hole is used in order to isolate the extreme events that contribute to the turbulent burst. The angle of sweep and ejection events are calculated at points around the island. The angle of events at these points depict the pattern similar to scouring/ deposition at points around the island in the braided river model.

3 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the quadrant method to analyze the turbulence characteristics of flow around the island in a braided river model and found that the burst ratio is strongly related with the erosion/deposition characteristics around the braid bar.
Abstract: Turbulent flow characteristics around the braid bar are not thoroughly studied till now. In the current paper, the quadrant method is used to analyze the turbulence characteristics of flow around the island in a braided river model. An attempt has been made herein to relate the depositional characteristics around the island in the braided river model to the sweep and ejection events. The new parameter bursting ratio is defined in this paper; it is observed that the bursting ratio is strongly related with the erosion/deposition characteristics around the island in a braided river model. The transition probability of 16 possible bursting movements are computed for four different experimental condition, the results shows that the, movements are closely related with the erosion/deposition magnitude around the bar in a braided river model. The values of sweep ratio and ejection ratio at 12 different points around the island for four different experimental conditions are computed using Box Cox analysis....

2 citations

Journal ArticleDOI
TL;DR: Characteristics of turbulent flow around a braided bar are much more complex as compared to the straight and meandering rivers as discussed by the authors, and the impact of a mid-channel bar on the turbulent flow structure has b...
Abstract: Characteristics of turbulent flow around a braided bar are much more complex as compared to the straight and meandering rivers. The impact of a mid-channel bar on the turbulent flow structure has b...

2 citations

01 Jan 2012
TL;DR: Rennie et al. as mentioned in this paper used a Doppler current profiler (aDcp) bottom track (Doppler sonar) to measure bedload flux pathways during two sequential aDcp spatial surveys conducted in a Rees River, New Zealand braid bar diffluence-confluence before and after a major flood event that inundated the entire braid plain.
Abstract: Maps of apparent bedload velocity are presented along with maps of associated channel change. Apparent bedload velocity is the bias in acoustic Doppler current profiler (aDcp) bottom track (Doppler sonar) due to near-bed particle motion (Rennie et al. 2002). The apparent bedload velocity is correlated to bedload transport (Rennie and Villard 2004), and thus serves as an indicator of local bedload transport. Spatially distributed aDcp surveys in a river reach can be used to generate maps of channel bathymetry, water velocity, bed shear stress, and apparent bedload velocity (Rennie and Church 2010). It is possible to relate the observed spatial patterns of bedload and forcing flow. In this paper, the technique is used to measure bedload flux pathways during two sequential aDcp spatial surveys conducted in a Rees River, New Zealand braid bar diffluence-confluence before and after a major flood event that inundated the entire braid plain. The aDcp surveys were complemented with terrestrial laser scans (TLS) of the bar topography. Linking aDcp bathymetry and TLS topography allowed for generation of complete digitial elevation models (DEMs) of the reach, from which morphological change between surveys were determined. Most intriguingly, the primary bedload pathway observed during the first survey resulted in sufficient deposition during the major flood event to fill and choke off an anabranch. This is perhaps the first direct field measurement of spatially distributed bedload and corresponding morphological change.

2 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20212
20202
20192
20184
20171
20151