40 



THEORY OF SEAKEEPING 



3 4 5 G 7 8 9 

 T 



2 3 4 5 6 7 S 9 10 II 12 

 T 



! 



Cc) 



i\ v = 10.5-ll.4'"/s, 



3 4 5 6 7 8 9 10 II 12 13 

 T 



15 



-t- 10 

 c 



u 



i- 



CL 3 



2 3 4 5 G 7 6 9 10 II 12 4 5 G 7 8 9 10 II 12 13 14 15 6 7 8 9 10 II 12 13 14 15 IG 



f T T 



Fig. 41 Observed frequency distribution of apparent periods of waves at different wind speeds. T denotes 

 the mean period computed from spectrum, Tb the observed mean period (from Neumann, 1954) 



Table 8 Characteristics of Fully Arisen Sea 



T = average "period" (seconds). 



Ttnax = period of most energetic wave in the spectrum. 

 H^yg Hu3, Hmo = height of average, 'A highest and Vio liighest 

 waves (range of significant periods: see Table 9). 



Table 9 Significant Range of Periods in Fully Arisen Sea at 

 Different Wind Velocities, V 



upper limit of significant periods) 



V, Tl, Tu, 



Ivnots sec sec 



The wave heights of a fully developed sea, resulting 

 from the foregoing relationships for different wind 

 speeds, are shown in Table 8. Attention should be called 

 to the fact that the Jorm of the spectrum and its area, 

 the ciuantity E, ha^'e been dcri-\'ed ciuite independently, 

 and therefore should be \'erified independently. The 

 form was based in Fig. 36, while the quantity E was 

 computed from the \'isually observed wa\'e heights in 

 Fig. 40. The dependence of energy E on wind speed to 

 the fifth power was obtained in the process of developing 



