As B. approaches infinity, this equation reduces to 



' = 2 g 



m c.g.s. 



units or to 



0.285V 



(30) 

 (31) 



where v is in knots. This is the average "period" of the fully developed 

 sea as shown by Pierson (1954). 



The function of Bi in equation (Z9) can be evaluated and used to 

 determine T for a partially developed sea. Let the term in brackets 

 in equation (29) be F (BJ. Then equation (29) becomes 



f= 0.285v.F{)3i). 

 The values of F ( BJ are given below in table 8. 



Table 8 



F ( B;) as a function of B . . 



<- 1 



Fronn the duration or fetch curves on the co- cumulative spectra given 

 by Pierson, Neumann, and James (1955), the values off. and v for a 

 particular weather situation can be determined. The use of table 8 above 

 then permits a computation of the average "period" of the waves. 



If B. is low (less than 0.5), the value of T can be approximated 

 from equation (26) in a more direct way. The exponential term under 

 the integral can be expanded in series with the resudt that 



T 



CO 



I 



n -0 



-I)" (20)^ 2n -1-4 

 nl T 



dT 



Ti ^ ( .1)" (2o)" 2n f2 



y. 



(33) 



34 



