明渠湍流对数律的诊断函数分析  

Diagnostic function analysis of the logarithmic law in open channel turbulence

作　　者：钟强 郑枫川 杨宇晨 邓兆宇 ZHONG Qiang;ZHENG Fengchuan;YANG Yuchen;DENG Zhaoyu(College of Water Resources and Civil Engineering,China Agricultural University,Beijing 100083,China;Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System,China Agricultural University,Beijing 100083,China)

机构地区：[1]中国农业大学水利与土木工程学院 [2]中国农业大学北京市供水管网系统安全与节能工程技术研究中心

出　　处：《清华大学学报（自然科学版）》2019年第12期999-1005,共7页Journal of Tsinghua University(Science and Technology)

基　　金：国家自然科学基金项目(51809268);北京市大学生创新性实验计划(2018bj103)

摘　　要：明渠水力学的传统观点认为,明渠湍流平均流速分布的对数律是与Reynolds数和Froude数无关的普适律。由于Karman常数与摩阻流速难以分离,且平均流速分布与对数律的偏离是一个渐进过程,因此导致目前对对数区的范围以及Karman常数的取值存在较大争议。该文引入诊断函数分析了高频粒子图像测速系统(PIV)测量所得光滑明渠恒定均匀湍流数据。当平均流速分布严格满足对数律时,诊断函数为常数。分析结果表明,在该实验的Reynolds数条件下,诊断函数在全水深都不存在水平段,即平均流速分布没有严格意义的对数区。根据实验和直接数值模拟的结果趋势推测,随着Reynolds数增加,流速分布将会出现严格意义的对数区,并且其范围会逐渐增大。当Reynolds数足够大时,明渠湍流的Karman常数将落在0.334和0.415之间,对数区范围将小于76<y4<0.5Re。The logarithmic law is generally accepted to be a universal law for turbulent open channel flows independent of the Reynolds number and Froude number.However,the thickness of the logarithmic area and the value of the Karman constant are still being debated due to the inseparability of the Karman constant and the friction velocity and the gradual changes in the relationship between the mean velocity distribution and the logarithmic law.A diagnostic function is developed in this study to separate the Karman constant and the friction velocity in particle image velocimetry(PIV)data for open channel flows.The diagnostic function for the experimental data shows that the mean velocity distributions have no strict logarithmic region.According to the results of experiments and direct numerical simulation(DNS),the logarithmic region appears only when the Reynolds number is large enough and is within 76<y4<0.5Re.The Karman constant is then between 0.334 and 0.415.

关 键 词：明渠 湍流 REYNOLDS数 对数律 诊断函数 

分 类 号：TV131.2+1[水利工程—水力学及河流动力学]