明渠水流的紊动特性

The Turbulence Characteristics of Open Channel Flow

本文采用先进的二维激光流速仪系统地量测了明渠水流的紊动特性,探讨了明渠水流的紊动机理。根据实测资料,得出了各种紊动统计参数的数学表达式,为研究水流的紊动结构及悬移质泥沙的运动机理提供了可靠的验证资料。

The turbulence characteristics of open channel flow has been measured by means of the two-dimensional laser doppler anemometer and the turbu-lence mechanism has been discussed. According to the measured data, the expressions of various statistical parameters are obtained. 1. The averaged-time velocity for clear water on smooth bed is cor-responding with logarithm distribution. 2. The turbulent intensity of longitudinal fluctuating velocity at Y<0.4 agress with Γ distribution, and linear distribution at Y>0.4. The turbulent intensity of vertical fluctuating velocity along water depth is in accordance with Rayleigh distribution. 3. The Reynolds stress at Y<0.4 and Y>0.4 accords with Γ distri-bution and linear distribution respectively. 4. Probability density of fluctuating velocity in two directions a Y <0.1 is corresponding with normal distribution, and Rayleigh distribution at Y>0.l approximately, of which the parameters are related to flow mixing length. The joint probability density of fluctuating velocity in two directirns is also described by two-dimensional normal probability density function. 5. Energy spectrum density of longitudinal fluctuating velocity damps with -1.8 power of frequency, and vertical one is inverse to frequ-ency. The results of this paper provide the reliable and verifiable data for the investigation of the turbulence structure and the suspension mechan-ism of sediment.