532 



30 



FIGURE 3. A sequence of spectra for the initial stage 

 of the generation of wind waves , showing the growth of 

 initial wavelets at a constant frequency of about 15 

 Hz, and the transition to irregular wind waves. The 

 spectra were calculated by the Maximum Entropy Method, 

 and each line represents an ensemble average of eight 

 cases. The fetch was 8 m and the nominal wind speed 

 was 5.1 m/s. [Cited from Kawai (1977).] 



20 



N 



10- 



Experiment 



• F=3m. NS=1 ' 



e. 6 1 Ex. I 



o 9 1 _ 



X 8 8 Ex.n 



Theory 



□ Ui/u, =5.0 

 ^ 8.0 



£ 





K-^ 





10 



u» (cm s-') 



20 



30 



FIGURE 4. Observed theoretically predicted frequency 

 of the initial wavelets, f., as a function of the 

 friction velocity of air, u^. Theoretical values are 

 for the condition of the maximum growth rate, where 

 Uj/u^ represents the dimensionless thickness of the 

 viscous boundary layer of the air. [Cited from Kawai 

 (1977).] 



10 20 



u, (cm s"' ) 



30 



FIGURE 5. The growth rate of the initial wavelets, 

 S, as a function of u^. Theoretical values correspond 

 to those for waves of the maximum growth rate. [Cited 

 from Kawai (1977) . ] 



