Recent ReseaTeh on Ship Waves 



Fig. 5 Aerial oblique view of the UNCATENA from 

 ahead of the bow 



from the center of the wake, which, in principle, should lie on the 

 cusp line or boundary of the wave systena. The apex of this center 

 is to some extent arbitrary, since, without further knowledge of the 

 .amplitude function A{0) , as it appears in Eq, (6), for this particular 

 vessel, the location of the ship's bow relative to the origin of the 

 (x,y) coordinates is arbitrary. It is clear, in fact, from Fig, 3 that 

 the apex of the UNCATENA cusp lines is somewhat ahead of its bow, 

 by a distance of about one ship length. This conclusion is consistent 

 with other observations of ship waves (e.g. , Gadd [ 1969]), and we 

 emphasize here that, in principle, there is no contradiction between 

 this observation and the linear Kelvin prediction. 



Also shown in Figs. 3 and 4 is a typical pair of 35°i6' angles, 

 which should be tangent to the wave crests on the cusp lines. Both 

 the i9°28' boundary angle and the 350i6' wave crest angle are sub- 

 stantially confirmed by these observations, within the accuracy 

 obtainable from these photographs. In fact, we have not observed 

 any phenomena in these tests which are inconsistent with the linear 

 Kelvin description of the far-field waves, in spite of the obviously 

 nonlinear near-field disturbance associated with this vessel, espe- 

 cially at its bow. There is also no noticeable effect on the waves 

 from the ship's viscous wake and propeller wake region, in spite 

 of the persistence of this wake far-downstream. (However, the 

 latter wake effects may be expected to affect the transverse waves 

 near the centerline; this effect could not be detected here because of 



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