刚性淹没球冠状植被水流特性试验研究

摘要

本文将植被体型概化为由球状树冠和主干组成的树状植被,采用MicroADV测量了树状植被影响下明渠水流的流速分布,分析了不同流量和水深条件下4组树状植被对明渠水流的影响,着重研究了树状刚性植被水流的平均流动和紊动结构,比较了多个典型位置处水流的纵向流速、垂向流速以及紊动强度.试验结果表明,水深越小,无量纲纵向流速越大;树冠的形状对水流特性的影响较大,在树状植被附近,纵向流速的垂向分布在树干层近似均匀分布,在树冠层先减小后增大,在无植被层符合对数分布;紊动强度在树冠层较大,在树干层和无植被层较小;通过象限分析,发现下扫作用主要在植被层起主导作用,喷射作用主要在自由水层占主导.%The tree-like canopy model,formed by crown and trunk,are conducted in laboratory flow experiments.MicroADV are used to study the flow characteristics influenced by vegetation with ball-like canopy in open channel.Flow condition varied in four cases,with different flow rate and water depth.Focusing on the mean velocity and turbulence structure,the vertical profiles of longitudinal velocity,vertical velocity and turbulence intensity were analyzed.The results show that the normalized longitudinal velocity increases as the water depth decreases.The longitudinal velocity is almost constant in the stem layer.It decreases firstly then increases with increment of depth in the canopy layer.Strong fluctuation of turbulence intensity is found in the canopy layer.The longitudinal velocity in no-canopy layer follows logarithmic law.The quadrant analysis recovers the canopy layer is the sweep-dominated area and no-canopy layer is the ejection-dominated area.