Diagnostic function analysis of the logarithmic law in open channel turbulence

doi:10.16511/j.cnki.qhdxxb.2019.22.036

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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 Re_τ. The Karman constant is then between 0.334 and 0.415.

Keywords open channel turbulent flow Reynolds number logarithmic law diagnostic function

Issue Date: 19 December 2019

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	ZHONG Qiang
	ZHENG Fengchuan
	YANG Yuchen
	DENG Zhaoyu

Cite this article:

ZHONG Qiang,ZHENG Fengchuan,YANG Yuchen, et al. Diagnostic function analysis of the logarithmic law in open channel turbulence[J]. Journal of Tsinghua University(Science and Technology), 2019, 59(12): 999-1005.

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http://jst.tsinghuajournals.com/EN/10.16511/j.cnki.qhdxxb.2019.22.036 OR http://jst.tsinghuajournals.com/EN/Y2019/V59/I12/999

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