The evolution of fluvial systems is greatly impacted by mid-channel bars, a typical morphodynamic process in natural rivers. Sometimes, the growth of vegetation over these bars complicates the morphological behaviour by interacting with the flow. It is therefore necessary to have a fundamental interpretation of the flow-turbulence structure around the mid-bar in presence of vegetation cover in order to understand braiding dynamics, still studies in this area are scarce. The present study investigates the process-form-vegetation-interaction through experimental investigation at a flume scale mid-channel bar model with different natural vegetation cover arrangements (paddy, leafy, and rigid stem). The flow-turbulence behaviour has been observed through the bifurcated channel using the three-dimensional Acoustic Doppler Velocimeter (ADV). Results showed that the longitudinal velocity component varies with the different vegetation cover, and it was highest with leafy vegetation (about 32%). Similarly, the Reynolds Stress and Turbulence Intensity were also observed to be higher in case of leafy vegetation. A unique pattern of flow-turbulence parameters was observed near the bar level, the lower canopy level, and the upper canopy level. Moreover, it was found that vegetation structure and its flexible nature influence both longitudinal velocity reduction and momentum transfer at and over the canopy, as well as the thickness of the shear layer region.

中文翻译：

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探索植被中部河道坝对分叉河道流动和湍流的影响：一种实验方法


河道中坝是自然河流中典型的形态动力过程，对河流系统的演化影响很大。有时，这些条上植被的生长通过与水流的相互作用使形态行为变得复杂。因此，有必要对存在植被覆盖的中坝周围的流动-湍流结构进行基本解释，以了解编织动力学，但该领域的研究仍然很少。本研究通过在具有不同自然植被覆盖排列（水稻、叶状和刚性茎）的水槽规模的河道中部坝模型上进行实验研究，研究了过程-形式-植被相互作用。使用三维声学多普勒测速仪 (ADV) 通过分叉通道观察了流动湍流行为。结果表明，不同植被覆盖度的纵向速度分量不同，其中叶状植被的纵向速度分量最高（约32%）。同样，绿叶植被的雷诺应力和湍流强度也较高。在条形水平、较低的冠层水平和较高的冠层水平附近观察到了独特的流动-湍流参数模式。此外，还发现植被结构及其柔性性质影响树冠处和树冠上的纵向速度降低和动量传递，以及剪切层区域的厚度。