The vertical distribution of longitudinal velocity and the turbulence structure of open channel flows with natural-like reedy emergent vegetation were investigated in this study. The natural-like reedy vegetation consisted of a basal stem and flexible blades with shape and reconfiguration behaviour comparable with those found in actual riparian areas. The 3D velocity field was measured using an acoustic Doppler velocimeter. The vertically non-uniform distribution of the frontal area could dramatically affect the exchange of mass and momentum between emergent vegetation and their surroundings. The average time velocity profile varied inversely with the frontal area. The high velocity gradient appearing at the middle section of the zone with frontal area varied considerably. The structures of vortices and vertical transport were analysed using spectral analysis and conditional sampling to identify the prominent vortical structures and their contribution to momentum transport. Spectral analysis suggested that the stem-scale vortices set by stem spacing where the vertical frontal area had no clear change were dominant, and shear-layer vortices where vertical frontal area dramatically changed cannot be disregarded. Quadrant analysis showed that inward and outward interactions were the dominant contributors to Reynolds stress, excluding the zones approaching the channel boundary and the vertical frontal area that dramatically changed. A four-layer model was developed to predict the vertical distribution of longitudinal velocity with a newly established profile of local drag coefficient. The predicting results agreed well with the experimental data.

中文翻译：

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含芦苇突生植被的明渠水流湍流结构及纵向速度分布

研究了具有类天然芦苇突生植被的明渠水流纵向速度垂直分布和湍流结构。类似自然的芦苇植被由基部茎和灵活的叶片组成，其形状和重新配置行为与实际河岸地区的相似。使用声学多普勒测速仪测量 3D 速度场。锋面区域的垂直非均匀分布会极大地影响出水植被与其周围环境之间的质量和动量交换。平均时间速度分布与额叶面积成反比。锋面带中段出现的高速梯度变化较大。使用光谱分析和条件采样分析了涡旋和垂直输运的结构，以确定突出的涡旋结构及其对动量输运的贡献。光谱分析表明，垂直锋面面积没有明显变化的茎间距设置的茎尺度涡占主导地位，垂直锋面面积发生显着变化的剪切层涡也不能忽视。象限分析表明，向内和向外的相互作用是雷诺应力的主要贡献者，不包括接近河道边界的区域和急剧变化的垂直锋面区域。开发了一个四层模型来预测纵向速度的垂直分布，并使用新建立的局部阻力系数剖面。