風波・植生開水路流れの組織乱流構造に関する実験的研究

Abstract

Enviromental problems about aquatic plants are now increasing in actual rivers. Coherent turbulence events such as ejections and sweeps are generated by the shear instability near the boundary between above-canopy layer and within-canopy layer. When wind-induced water-waves appear on the free-surface flows, a large amount of oxygen gas may be transported toward the vegetation layer, and it is infer red that the mass and momentum exchanges are promoted significantly by the coherent motions. It is thus very important in river environment to investigate these turbulence structure and coherent motions in such flows. In this study, we conducted turbulence measurements by using a high-speed PIV technique. It was found from time-averaged velocity profiles that some wave effects appear even in the canopy layer. The correlation analysis was also conducted in order to examine turbulence transport process promoted by the wind-induced air/water interface. Furthermore, relation between the coherent event and waves were revealed on the basis of the present PIV data.