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SURFACE DEFORMATION EFFECTS ON THE FREE-SURFACE TURBULENCE STRUCTURE IN HIGH-Fr OPEN-CHANNEL FLOW

Yoshinobu Yamamoto
Department of Nuclear Engineering, Kyoto University, Yoshida Sakyo-ku, Kyoto 606-8501,Japan

Tomoaki Kunugi
Department of Nuclear Engineering, Kyoto University, Kyoto Daigaku-Katsura, Nishikyo-ku, Kyoto, Japan

Shin-ichi Satake
Department of Applied Electronics, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 Japan

Abstract

In this study, we succeed in a direct numerical simulation (DNS) of a high-Fr turbulent open-channel flow at a Froude number of 1.8 and a Reynolds number of 2325 based on a bulk velocity, the gravity acceleration, a water depth and the kinetic viscosity, by means of the multi-interfaces advection and reconstruction solver (MARS) method, and the DNS database such as the mean velocity, turbulent statistics and surface fluctuations were obtained. At the free-surface, surface waves are constructed of large-scale gently bumped waves with the maximum wave-height approximately corresponding to 4% of the water depth and the small scale isotropic waves caused by surface fluctuations. Wall-normal turbulent intensity and energy-dissipation rate were increased toward the free-surface. These tendencies of turbulent statistic quntities near the free-surface were in good agreement with experimental measurement results by using a laser doppler anemometer (LDA) (Nakayama and Nezu, 1999). Although increase of vertical turbulent intensity, the redistribution of turbulent intensity from vertical component to streamwise one is predominant near free-surface in high-Fr flow. It is similar to a low-Fr flow.