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Effects of Free-Surface Shear on Coherent Hairpain Vortex Genereted Near Flume Bed

Author(s): Michio Sanjou; Iehisa Nezu

Linked Author(s): Michio Sanjou

Keywords: Coherent structure; Wind-induced water waves; PIV measurements

Abstract: Large amounts of oxygen gas and heat are often transported toward the river bed through the interface between water and wind layers. Wind-induced water waves promote significantly such environmental and physical processes. In contrast, the bed zone is a kind of turbulent boundary layer, where turbulence is generated and transported associated with the production of bed shear stress. Particularly, coherent hairpin vortices are formed together with strong ejection events toward the outer part of the layer, and they promote mass and momentum exchanges between the inner and outer layers. Such a near-wall turbulence may be influenced strongly by these air/water interfacial fluctuations accompanied by free-surface velocity shear and wind-induced water waves. However, there are a lot of uncertainties about wind effects on the wall turbulence structure. To address these topics, we conducted particle imagery velocimetry (PIV) measurements in open-channel flows combined with air flows, in order to investigate the effects of air/water interactions on turbulence structure through the whole flow depth region.


Year: 2010

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