Mooring and Positioning of Vehicles in a Seaway 



The Newmann wave spectrum for a unidirectional fully- 

 developed sea represented by 



.2, . ^ -6 -Zg^AoiV^)^ 

 A (co) = Ceo e (43) 



where C is an empirical constant having the value 51,5 ft /sec , 

 Vw is the wind speed in units of ft/sec, and A (oo) has the units 

 ft^-sec. The wave spectrum for a non- unidirectional sea,^ allowing 

 for angular variation (a two-dimensional spectrum), is represented 

 by 



2 2 



— Co) e cos p^, for -•y<p^< +-7, 0<co< +00 



A^co,PJ = ^ 2 2 



0, otherwise, (44) 



where Pyy is an angle measured from the direction toward which the 

 wind is blowing (the predominant wave direction). In this case, 

 the motion spectrum occurring for a particular barge heading Pg, 

 measured relative to the wind direction is 



^('•'Mco) = A^co)M dpv,cos2p^|Ti_((o,P)|2 (45) 



where P = Pv«~ Pb' ^^^ ^^^^ energy spectrum will depend upon the 

 angle Pg. 



From the spectral density function, ^ ' (co) , for a particular 

 motion, there may be obtained, in principle, all the statistical or 

 probabilistic properties possessed by the random process. The 

 total area, Ej, under the spectral density function curve, as defined 

 above , 



1037 



