基于掺长理论的淹没柔性植被水流流速分布研究

Study on Velocity Distribution of Flow With Submerged Flexible Vegetations Based on Mixing-Length Approach

采用PVC薄片对柔性植被进行了模拟,并用三维Micro ADV对淹没柔性植被恒定水流进行了实验测量,获得了水流纵向流速和Reynolds切应力的分布.实验结果表明,淹没柔性植被水流植被层和非植被层的水力特性有显著不同.在非植被层,Reynolds应力为直线分布,而时均流速则符合经典的对数律分布.基于新"河床"的概念,首次提出用河道压缩参数来表示植被对水流的影响,并合理假设了一个新的混合长度公式,由此得到的时均流速公式相比前人的成果有所需参数少、计算简单及实用性强等优点.

Choosing PVC slice to simulate the flexible vegetation, the laboratory experiments were carried out in an open channel with submerged flexible vegetation, and 3D acoustic Doppler velocimeter （Micro ADV） was introduced to measure the local flow velocities and Reynolds stress. The result showed that the hydraulic characteristics in the non-vegetation layer and the vegetation layer are totally different. In the region above the vegetation, Reynolds stress＇ s distribution is linear; meanwhile, measured velocity＇ s profile is a classical logarithmic one. Based on the concept of nwe ＂riverbed＂, the river compress parameter which represented the impact of vegetation on river was given for the first time and a new mixing length expression was assumed with reason. The formula of time-averaged velocity deduced from the mixing length expression had advantages of less parameters needed, simple calculation and useful application.