含柔性植被明渠水流水力特性的试验研究

Experimental study on hydraulic characteristics of open channel with flexible vegetation

采用粒子图像测速(PIV)技术对含柔性淹没植被明渠水流的水力特性进行试验研究。利用人造水草模拟天然柔性植被,对不同密度、不同流量条件下含柔性植被明渠恒定均匀流场进行了测量,得到了淹没植被情况下纵向流速、雷诺应力、紊动强度沿垂向分布与曼宁系数的变化情况。试验结果表明:纵向流速的垂向分布可以分为3区,包括自由水面区、中间冠层区和近床面区。自由水面区流速随植被密度增大而增大,中间冠层区与近床面区流速随植被密度增大而减小。雷诺应力与紊动强度的峰值出现在植被冠区顶部附近,并随着植被密度增大而增大。

In order to understand the hydraulic characteristics of the water flow in open channels with submerged flexible vegetation,experiments were carried out using the particle image velocimetry(PIV)method.The synthetic aquatic vegetation was used in place of natural flexible vegetation,and the constant water flow velocity field of the open channel with this vegetation was measured under different vegetation density and flow conditions,form which the longitudinal velocity,Reynolds stress,turbulence intensity along the vertical distribution and the variation of Manning coefficient were obtained under the condition of submerged vegetation.The test results show that the distribution of the longitudinal velocity can be divided into three zones,which are the free water zone,the middle canopy zone and the near bed zone.The flow velocity in the free water zone increased with the vegetation density,whereas it decreased with the increase of the vegetation density in the middle canopy zone and the near bed zone.The peak values of Reynolds stress and turbulence intensity appeared around the top of the vegetation crown and increased with vegetation density.