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You are here : eLibrary : IAHR World Congress Proceedings : 35th IAHR Congress - Chengdu (2013) : THEME 5 - FLUVIAL HYDRAULICS AND RIVER MANAGEMENT : Turbulent Structure in the Inner Layer of the Open Channel
Turbulent Structure in the Inner Layer of the Open Channel
Author : Shengfa Yang, Jiang Hu, Peng Zhang, Wenjie Li and Yang Chen
The turbulent structure continues to be one of the outstanding unsolved questions in the phenomenology of turbulence. In the high-precision experimental flume, a high-resolution measurement, the range of which being 10 mm * 10mm and the resolution being 0.2 mm * 0.2 mm, as well as a low-resolution one, the range of which being 25 mm * 32 mm and the resolution being 1.0 mm * 1.0 mm, have been conducted in a uniform open channel of 32mm water depth using PIV to measure the turbulent structures. The turbulent structures in the inner layer of open channel have been studied through PIV measurement data and the main understandings are as follows: 1) As the single-point statistical sample, the profiles of mean velocity, fluctuating velocity standard deviation and Reynolds shear stress through PIV measurement data mainly agree with those from other researchers, demonstrating the good reliability of PIV measurement data. 2) The wall vortices are mainly in the sub-layer (u<15u ), the stream-wise scale * of wall vortices is 15-30y , the height of wall vortices is 6-30 y . The strength of down-flow zone in the * * log-law layer affects the height of wall vortices. 3)The log-law layer of open channels is basically composed of three uniform momentum zones with different directions, and the random and irregular velocity is generalized as a locally-regular uniform momentum zone. 4) This paper puts forwards a momentum exchange pattern in uniform momentum zones in which the up-flow zone and the down-flow zone form a sinusoidal contour and produce multiple hairpin vortices, forming hairpin vortices packets. starting from the momentum exchange pattern in uniform momentum zones of different directions, this paper generalizes the irregular flow of open channel turbulence as the flow in local uniform momentum zones and explains some basic theoretical problems about turbulent structures in the inner layer of open channel, such as the causes of wall vortices in the viscous sub-layer and hairpin vortices in the log-law layer, which provides some new ideas for the study on turbulent structures in open channel.
File Size : 789,410 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 35th IAHR Congress - Chengdu (2013)
Date Published : 18/07/2016
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