Although this paper concerns waves in deep water, the ways in which 

 current systems such as this increase the probability of extreme waves 

 is of direct relevance to any structural design for waters in which 

 strong currents occur. 



40. MIZUNO, S., and MITSUYASU, H. , "Effects of Adverse Winds on the 

 Phase Velocity of Mechanically Generated Water Waves," Reports of 

 Research Institute of Applied Mechanics^ Kyushu University, Japan, 

 Vol. XXI, No. 68, 1973, pp. 33-52. 



Keywords. Comparison of Theory and Measurement; Currents, Unidirec- 

 tional; Currents, Wind-Drift; Experiment; Wind Shear; Wind Velocity 

 Profile. 



Discussion. These are detailed measurements of the phase speed of 

 mechanically generated surface waves at different periods and strengths 

 of an opposing wind. The experiments were carried out in a wind-wave 

 tunnel 0.6 meter wide and 0.8 meter high. The glass test section was 

 13.4 meters long, and the maximum wind fetch about 8.5 meters. Water 

 depth throughout the experiment was 0.35 meter. Wave periods were 0.8, 

 1.0, and 1.2 seconds, and windspeeds ranged from 2.5 to 12.5 meters per 

 second. 



Wave measurements were made simultaneously at six locations with 

 resistance-type gages. The complex Fourier coefficients at the 

 fundamental frequency were used for calculating the amplitude and phase 

 of the waves. The phase speed of the waves was then determined from the 

 phase difference between any two stations. Wave heights ranged from 1.5 

 to 4.0 centimeters. Vertical wind profiles were measured with a 

 standard Pitot tube. The reference airspeed was that of the free 

 stream over the rough upstream transition plate. 



The surface-drift current was measured using small paper floats, 

 and the magnitude was about 3 percent of the reference airspeed, as 

 found by many other investigators. The hydrogen bubble technique pro- 

 vided the current profile In all experiments, the current became zero 

 about 7 centimeters below the water surface. 



Friction velocity and surface roughness were determined from the 

 wind profiles which were logarithmic. Friction velocity was somewhat 

 larger in the presence of the mechanically generated waves, except at 

 the downstream end of the tunnel. 



The phase speed of the waves decreased markedly with windspeed, 

 and the rate of decrease increased with decreasing wave period. The 

 latter observation is easily explained, since the smaller the period, 

 the more the wave motion takes part in the upper region, where the wind 

 drift is strongest. 



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