明渠恒定均匀流流速垂向分布研究

Study on vertical distribution of steady uniform flow velocity in open channel

恒定流是明渠水流基本原理研究的重要课题,水流的动力特性决定了泥沙的沉积和悬浮,河床底部侵蚀和沉积的演变,是水动力机理研究的重点。为了进一步讨论明渠平均流速剖面和恒定流摩阻特性,文章结合理论分析和实验研究,基于粒子图像测速仪(PIV)水槽实验系统,探究不同工况下恒定流流速剖面、紊流度和底边界层厚度等参数的变化规律。结果表明:(1)沿轴向,紊流度与平均流速成正相关,随着总水深的增加,紊流度沿垂向变化变缓。平均流速和比降的增大,都会使紊流度曲线右移。随着比降的增大,平均流速所引起的紊流度的增大幅度越小。但是,平均流速对比降引起的紊流度的增大幅度影响不大。(2)总水深较小时,平均流速对底边界层厚度的影响较大,总水深较大时,总水深对底边界层厚度的影响更明显。

Steady flow is an important topic in the study of the basic principles of open channel flow.The dynamic characteristics of water flow determine the deposition and suspension of sediment,evolution of erosion and deposition at the bottom of river bed,which was the focus of hydrodynamic mechanism research.In order to further discuss the average velocity profile and steady flow friction characteristics of open channel,based on the Particle Image Velocimetry(PIV)flume experimental system,theoretical analysis and experimental research were compared.The variation rules of steady flow velocity profile,turbulence and bottom boundary layer thickness under different working conditions were explored.The results show that:(1)Along the axial direction,the turbulence intensity is positively correlated with the mean velocity.With the increase of total water depth,the turbulence degree changes slowly along the vertical direction.With the increase of average velocity and gradient,the turbulence curve will shift to the right.With the increase of the gradient,the increase of turbulence intensity caused by the average velocity is smaller.However,the average velocity has little effect on the increase of turbulence intensity caused by the gradient.(2)When the total water depth is small,the average velocity has a greater influence on the thickness of the bottom boundary layer.When the total water depth is large,the influence of the total water depth on the thickness of the bottom boundary layer is more obvious.