Abstract
It has been pointed out that a turbulence structure near the free-surface has a close relationship with surface-wave fluctuations and the Froude number. In particular, a critical flow occurs when the Froude number is close to one, and the turbulence structure may become unstable. This phenomenon can be seen in the complexity of turbulence redistribution and the undulation property of surface-wave fluctuations. In this study, turbulence measurements were three-dimensionally conducted in open-channel flows by using two sets of fiber-optic LDA system, and simultaneously, the surfacewave fluctuations were measured by an ultrasonic depth-meter instrument. The aim of this study is to clarify the relationship between the turbulence structure near the freesurface and the surface-wave fluctuations
