Diagnostic function analysis of the logarithmic law in open channel turbulence
ZHONG Qiang1,2, ZHENG Fengchuan1, YANG Yuchen1, DENG Zhaoyu1
1. College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; 2. Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083, China
Abstract：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 < y+ < 0.5 Reτ. The Karman constant is then between 0.334 and 0.415.
钟强, 郑枫川, 杨宇晨, 邓兆宇. 明渠湍流对数律的诊断函数分析[J]. 清华大学学报（自然科学版）, 2019, 59(12): 999-1005.
ZHONG Qiang, ZHENG Fengchuan, YANG Yuchen, DENG Zhaoyu. Diagnostic function analysis of the logarithmic law in open channel turbulence. Journal of Tsinghua University(Science and Technology), 2019, 59(12): 999-1005.
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