天然河道水流紊动特性分析

Turbulent characteristics of flow in river

本文采用超声多普勒三向流速仪对不同流量级的条件下长江干流黄陵庙水文观测断面不同垂线的脉动流速进行了观测。根据现场观测资料,对水流的紊动周期、频率、概率密度函数等进行了定量的数学描述,并对时均流速、紊动强度、雷诺应力等沿垂线的分布规律进行了分析计算。结果表明,脉动流速的概率分布在充分发展的自由紊流区近似为正态分布,在近壁强剪切紊流区为偏态分布;各垂线紊动强度在相对水深大于0.4的范围内比较均匀,在接近河底处升高,达到最大值后迅速减小,至河底为零。

The turbulent velocity distributions along different vertical lines under various flow discharges in cross section of Huanglingmiao Hydrologic Station, located at the main stream of Yangtze River, are measured by using an Acoustic Doppler Current Profiler（ADCP）. The analyses of measurement data show that the probability distribution of fluctuating velocity in fully developed turbulent region is approximately in the form of Gaussian curve but it changes to skew distribution in the vicinity of riverbed where strong shear turbulence is taken place. The turbulence intensity is uniformly distributed in the range of relative flow depth bigger than 0.4, but it increases in the vicinity of riverbed and drops down sharply at the bottom.