174 



11M)R01)V.\AM1C;S 1\ sllll' Dl.SlGN 



Sec. 48.11 



wa-s puiiitctl "111 many years ago by Franz 

 (lorstiier, in his classic paper of 1802 on the 

 trochoidal wave, referenced in Sec. 48.18: 



"Sine* this llutiry of \vavo« is h.-t.-x"*! ii|)on tho cquality 

 of hydroslntic prp.isurp, it followH that all motions of the 

 »!it»^r which do not cluingc this uniformity of pressure, 

 neither disturb the wave motion. This makes it possible 

 for several waves of various sizes to cross in difTerent 

 dirwtions, and ronlinue their motion undisturbed, .\gain 

 genonU c.\|)crienco supplies ample verification. At the 

 e&ma time it explains the numerous elevations which 

 frequently ap|)onr at the surface of tho wat<ir" llOiiKli.^h 

 tran.<lation, Univ. of Cal., 1952, par. 16, p. 14]. 



Assuming tliat a ship is traveling through tliis 

 synthetic complex sea on a course of 70 cleg true, 

 there results the profile in diagram 1 of Fig. 48.1. 

 To emphasize the irregularities in surface eleva- 

 tion, the profile ordinatcs above and below the 

 undisturbed or quiet water level are magnified 

 6.308 times. 



.\t the origin, tho hcigiit of tho water "i.slct" 

 ai)ove the undisturbetl level is 4 + 3 + '- = 9 ft. 

 Close to this islet, toward the WSW, is a deep 

 iiole, extending G.4 ft below the undisturbetl water 

 level. Within 14.5 ft of the origin, therefore, one 

 (inds a difference in elevation of 15.4 ft. The 

 steepness ratio of the wave near the origin is of 

 the order of 1/18.7, as comjjared to steepness 

 ratios of 1,'30, 1/40, and l/oO for the components. 

 The maximum wave slope near the origin is 

 about 10 (leg. 



On either side- of this group of one high crest 

 .•mil two deep troughs, within 300 or 400 ft, the 

 waver level is relatively flat, with crests and 

 troughs less than 1.5 ft in magnitude. 



Following the composition of the synthetic 

 three-component wave at to , each wave is then 

 shifted to the position it would occupy at the 

 time <o + 3 sec, by the distance indicated in 

 Table 48. j. A new composite pattern is sketched, 



,'//ti \ 

 Fio. 48.H Contour Diackam m\\ Tiiuee Suruni'OBBo Sinuboidal Wavbh, 3 Seconos Latkr Than Fto. 48.0 



