Abstract

Turbulent structures of flow around the mid-channel braid bar have not been adequately investigated so far. Of late, the intrinsic fluvial hydraulics associated with the formation of braided rivers interspersed with sand bars have been vital topics of research. In this paper, the findings yielded from a research foray on the aforementioned underlying processes are presented. For obtaining the requisite experimental data, the three-dimensional flow velocity components are measured with the help of acoustic Doppler velocimetry (ADV) and these velocity data are analyzed using quadrant bursting techniques. The flow characteristics are greatly affected by the presence of a mid-channel bar. The depth-averaged contours of turbulent parameters are analyzed in the present study. Herein, the hole size concept is adopted for separating the bursting events. The effect of hole size on the quadrant events is also studied. The experiments are performed for different submergence ratios. A new parameter, Bursting Index (BI), is proposed in this research to reflect a quantitative measure of the turbulent bursting effect on streambed elevation changes. The parameter BI is the ratio of the odd event occurrence probability to the even event occurrence probability. The high values of correlation coefficients signify that the BI is profoundly influenced by streambed elevation changes, which makes it an ideal parameter for analyzing scour and deposition phenomena in real-life water management projects. The prime focus on performing the experiments has been to analyze the impact of bar height on flow structure in the vicinity of the mid-channel bar.

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