Effects of Bed Load Movement on Mean Flow Characteristics in Mobile Gravel Beds |
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| Authors: | Xianye Wang Qingyuan Yang Weizhen Lu Xiekang Wang |
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| Affiliation: | (1) State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, People’s Republic of China;(2) Department of Civil and Architectural Engineering, City University of Hong Kong, Kowloon, Hong Kong, SAR, People’s Republic of China;(3) State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610065, People’s Republic of China; |
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| Abstract: | The effects of bed-load movement on mean flow characteristics were experimentally investigated using particle image velocimetry
(PIV). The gravel beds associated with open-channel flow are hydraulically rough, and two types of grain with different median
diameters were used. The flow field and bed load motion images were simultaneously obtained via the particular experimental
setup. The mass of sediment particles instantaneously moving on the bed, i.e., the sand-wave, was observed in the experiment.
It was found that the sand-waves have an average friction angle of 11.2° and heights ranging from 2.2 d
50 to 3.8 d
50. The mean velocity profiles on the mobile bed can also be represented with logarithmic distribution with deviations occurred
in the near wall region. Based on the Schultz–Grunow formula, a modified equation is developed in this study to better express
the flow resistance factor in terms of the Reynolds number and the ratio of flow depth to roughness height. |
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