Study on mass transfer process and turbulence structure in open-channel flows with wind-induced water waves

当风出现在自由表面流动，如实际的河流和人工渠道，一个显着的速度剪切和水波附近的空气/水界面产生。可以推断，近壁区的发夹涡等相干湍流结构也受到这些界面波动的影响。然而，风对壁面湍流结构的影响还存在许多不确定性。在本研究的第一阶段中，PIV测量在明渠流动下的风，以揭示界面的自由表面条件的相干湍流结构和能量传递过程中的内外层的影响。在自然湖泊和海洋中观察到的风引起的水波会引起称为朗缪尔环流的二次流。在第二阶段，所有三个速度分量可以同时测量的立体PIV技术。利用多相机系统可以研究表面起伏与速度分量之间的相位关系、长径比对朗缪尔环流形成特性的影响等。

When wind appears over the free-surface flows such as actual rivers and artificial channels, a significant velocity shear and water waves are generated near the air/water interface. It is inferred that coherent turbulence structure such as hairpin vortex in the near-wall region is also influenced by these interfacial fluctuations. However, a lot of uncertainties remain about the wind effects on wall-turbulence structure. In the first stage of the present study, PIV measurements were conducted in open-channel flows under the wind flows in order to reveal the effects of interfacial free-surface condition on coherent turbulence structure and energy transfer process in the inner and outer layers. Wind-induced water waves observed in natural lakes and ocean cause secondary currents called as Langmuir circulation. In the second stage, all three velocity components could be measured simultaneously by the stereoscopic PIV technique. The present multi-camera system allowed us to investigate the phase relation between the surface fluctuation and the velocity components, effects of aspect ratio on formation properties of Langmuir circulation and so on.