Turbulence structure and coherent vortices in open-channel flows with wind-induced water waves |
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Authors: | Email author" target="_blank">Michio?SanjouEmail author Iehisa?Nezu |
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Institution: | (1) Institute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo 153-8505, Japan;(2) Department of Mechanical Engineering, Tokyo University of Science, Yamazaki 2641, Noda, Chiba 278-8510, Japan;(3) Department of System Design Engineering, Keio University, Yokohama 223-8522, Japan |
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Abstract: | When wind-induced water waves appear over the free-surface flows such as natural rivers and artificial channels, large amounts
of oxygen gas and heat are transported toward the river bed through the interface between water and wind layers. In contrast,
a bed region is a kind of turbulent boundary layer, in which turbulence generation and its transport is promoted by the production
of bed shear stress. In particular, coherent hairpin vortices, together with strong ejection events toward the outer part
of the layer, promote mass and momentum exchanges between the inner and outer layers. It is inferred that such a near-bed
turbulence may be influenced significantly by these air–water interfacial fluctuations accompanied with free-surface velocity
shear and wind-induced water waves. However, these wind effects on the wall-turbulence structure are less understood. To address
these exciting and challenging topics, we conducted particle imagery velocimetry (PIV) measurements in open-channel flows
combined with air flows, and furthermore the present measured data allows us to investigate the effects of air–water interactions
on turbulence structure through the whole depth region. |
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Keywords: | |
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