【作者】 雒天峰；

【导师】 吕宏兴；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2006， 硕士

【摘要】 明渠水流是对具有自由表面的水流在有限尺度的固体边界约束下流动现象的一种概化。现实中遇到的明渠流动大都是充分发展的紊流边界层流动,其流经的固体边壁均属粗糙床面。自尼古拉兹发现粗糙管水流的流速分布和阻力系数与光滑区的情况不同以来,许多学者相继进行了大量的试验观测和理论研究,但由于紊流本身结构的复杂性和过水断面、粗糙形式的多变性,即使简单的明渠流动,对其流动的描述目前还不尽完善。在重要问题上尚未得出公认的结论。在水资源日益紧缺的今天,引水明渠流量的精确度量是一个急需解决的实际工程技术问题。U形渠道在灌区应用广泛,但U形渠道流量测量仍处于发展阶段,断面测流技术迄今尚未解决。有些灌区对U形渠道测流时沿用梯形或矩形渠道的测流方法,导致测流精度低,对灌区用水调度管理影响大,也无法给出测流断面上正确的水位流量关系,从理论或工程角度都需要更为符合实际、准确的渠道流量计算方法。准确掌握明渠流速分布规律后,就可以根据流速分布规律特点,探索流量计算公式。本文在分析国内外学者对矩形渠道流速分布规律的研究基础上,对U形渠道进行试验研究。将实测流速资料分别从过水断面竖向和横向两个方向分析,利用尾流函数和指数分布公式进行拟合。得出在竖向,卡门常数k=0.41,取不同尾流强度系数Π=0、Π=0.2、Π=0.4、Π=0.6、Π=1、Π=1.5时,实测流速拟合曲线交于一点,根据交点处的水深,确定出在U形渠道0.2H(H表示渠道水深)处,可将过水断面分区讨论,在0≤y<0.2H(y表示测点水深)的范围为内区,流速可用线性公式表示;在0.2H<y≤H的范围内为外区,流速可用尾流函数修正后的对数公式表示;经过分析计算出的交点流速值与过水断面内的平均流速值,发现0.2H处的流速值与渠道平均流速相等。在横向利用指数公式,采用三种指数形式进行对比,找出了相对误差较小的流速分布公式。并确定了公式中的相应系数。分析现阶段流量测量的主要方法,结合流速-面积法的优点及U形渠道几何特性,利用推导出的流速公式,探索出了U形渠道的流量计算公式。更多还原

【Abstract】 Open channel flow is a sort of generalize for water flow phenomenon, which water stream with free surface be leashed by solid boundary with finity scale. In the fact, the open channel flow mostly is the turbulence-borderland flow. The solid boundary mostly belongs to roughness bed. Since nikuradse find the difference of velocity distribute and resistance coefficient between roughness pipe and smooth pipe, many scholar carry through a great deal of experimentation observation and theoretical analyse, but because the complexity of turbulence own structure and levity of water flow section、roughness former, even if simply open channel flow, it is don’t perfect to describe their flowing. There aren’t accepted conclusions on some important question.Nowadays, with the short of water resource increasingly, the precision measurement of discharging in open channel is an engineering technique problem to exactly resolved,The open channel with U-shape cross-section are extensively used in irrigational district, however the methods of measurement for discharge is on seedtime, and the technology of section measure didn’t resolved. The methods of measurement for discharge in trapezia or rectangle channel are being used to channel with U-shape cross-section. Insult in the measurement precision of discharge is very low, lead to greatly influence of attempter supervise in irrigational district, and don’t give the correct relation between water level and discharge. From the theoretic or engineering facet, its need to find more practicably and exactly calculates methods for discharge. After griped velocity profile distribute, try to find the formula for calculate discharge from its character.This thesis based on the analyses of rectangle channel distribute low by scholars of home and abroad, make an experimentation into channel with U-shape cross-section. To analyzed the practical velocity data from vertical and orientation of water across section, carry through simulate with the wake-stream function and exponential equation .Educed,k=0.41 choose different wake steam intensive parameterΠ=0、Π=0.2、Π=0.4、Π=0.6、Π=1、Π=1.5, the simulative curve of practical velocity intersect one point, basis depth of point , water across section can divided two part around 0.2H in channel with U-shape cross section .Its the in-part at 0≤y<0.2H range, velocity can be express by linearity equation, and its the更多还原