Sea surface current effects on the growth of wind wave in laboratory experiment

Chiaki Tanaka1, Naoya Suzuki2, Naohisa Takagaki3, Yuliya I. Troitskaya4, Satoru Komori5,6, Alexander Kandaurov7, Maxim Vdovin7 and Masanori Konda8, (1)Kindai University, Graduate school of Science and Engineering, Osaka, Japan, (2)Kindai University, Department of Mechanical Engineering, Osaka, Japan, (3)University of Hyogo, Department of Mechanical Engineering, Himeji, Japan, (4)Institute of Applied Physics RAS, Nizhny Novgorod, Russia, (5)Doshisha University, Highly-Functional Nano-Particle Research Center, Kyoto, Japan, (6)Japan Agency for Marine-Earth Science and Technology, Center for Earth Information Science and Technology, Kanagawa, Japan, (7)Institute of Applied Physics RAS, Russia, (8)Kyoto Univ, Kyoto, Japan
Abstract:
Sea surface currents may have an affect the growth of wind waves and air-sea momentum transfer. In this study, we investigated the Doppler shift of the wind waves due to the surface current by reproducing the wind wave together with the surface current using a wind wave tank. The vertical distribution of the wind velocity and the wave height were measured using a pitot tube and a wave gauge, respectively. The imposed conditions: wind speeds of 1.92, 6.70, 11.7, 15.84, and 21.91 m/s; and surface current speeds of 0.036, 0.073, 0.110, 0.146, and 0.180 m/s. We also used data from different wind wave tanks, in Russian Academy of Science, Russia, and in Kyoto University, Japan. The wind velocity of the boundary layer in the air increased with the surface current velocity. In the wind wave spectrum, the peak frequency of the wind wave corresponded with increase in the surface current. Conversely, the spectral density decreased. These results show that the surface current influences the growth of the wind wave. In the case of the high wind speed, the development of the wave height is suppressed by wave breaking, but the development of the wavelength is not suppressed. Moreover, we found that the wavelength is affected by the Doppler shift due to the surface current, as in the case of low wind speed. We also investigated in detail the effect of the surface current on the growth of the wind wave by measuring the Reynolds stress using PIV (Particle Image Velocimetry) and the vertical distribution of the velocity in the water side using LDV (Laser Doppler Velocimeter).
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