STUDY ON RELATIONSHIP BETWEEN TURBULENCE STRUCTURES AND WATER SURFACE FLUCTUATIONS IN WIND-DRIVEN OPEN-CHANNEL FLOWS

Abstract

The present study describes an experimental relationship between turbulence structures in water layer and the water-surface fluctuations in wind-driven open-channel flows by using both a laser Doppler Anemometer (LDA) and a wave gauge simultaneously. The purpose of this study is to make clear the characteristics of surface fluctuations on water dynamics in air-sheared open-channel flows, and to evaluate the effects of surface fluctuations on vertical momentum transport in the water layer. As the results of experiments, it is shown by spectral analysis that the velocity fluctuations near the interface in both only open-channel flow and wind-driven open-channel flow are significantly affected by the water surface in every range of frequency, and that there exists a high correlation between turbulence near the air-water interface and the surface fluctuations in a predominant frequency due to high-sheared wind flow. Moreover, it is recognized by wavelet analysis that the turbulence structures in weak wind-driven open-channel flows are governed by both wall shear and wind-induced flows.