明渠水流湍流结构的试验研究

本文采用二维激光流速仪(2D-LDA)在玻璃水槽中实测了光滑和加糙壁面上清水的湍流结构和时均结构。通过试验观测并结合其它学者的资料,研究了水流时均流速分布。发现加糙壁面的流速分布在半对数坐标中为一连续曲线,通过调整理论床面将坐标起点下移后可转变为直线,与对数分布吻合。文中对雷诺切力分布进行了分析并给出了最大雷诺切力及其出现位置的计算公式。实测切力分布与理论公式计算值基本一致,实测表明:边壁加糙对雷诺切力分布影响不大,光滑边壁与加糙边壁切力分布基本相同。文中还讨论了壁面加糙对纵向和垂向脉动强度分布的影响,认为主流区纵、垂向脉动强度均可近似地视为线性分布。

AN EXPERIMENTAL STUDY OF TURBULENT STRUCTURE IN OPEN-CHANNEL FLOW

A 2-D Laser Doppler Anemometer was used to measure theturbulent and time-averaged structure of clean water in a flume with glasswall over smooth and rough beds.Combining with Other researcher's data,we studied the mean velocity distribution with the experiments.It wasfound that the velocity distributions over rough beds are continuous curvesin the semi-logarithmetic co-ordinates and can be changed into straightlines to be fit for the Log Law through adjusting the theoretical bedsurface and shifting the origin of the vertical ordinate under the topof the measured particle.The turbulent stress distribution was ana-lysed,and the formula calculating the maximum stress value and its posi-tion were given in the paper.The stress distributions obtained fromreal measurment and theoretical calculation are almost same.The measuredresults show that the influence of the rough bed on turbulent stressis small and the distributions on the smooth and rough beds are similar.The influence of rough bed on the longitudinal and vertical fluctuationintensities was also discussed in this paper.It is thought that the bedroughness has no effect on the longitudinal and vertical distributions ofdimensionless with the friction velocity u, and the longitudinal andvertical distributions of fluctuation intensities are approximate linear.