Salvesen 



Fig. 15 - Wave resistances 

 for 1.50-ft submergence 



Another interesting result is that the waves start to break at submergences 

 smaller than 1.25 ft. This can clearly be seen from the wave profiles plotted in 

 Fig. 16 and from the pictures shown in Fig. 17, both for 1.0-ft submergence 

 (about three times the thickness of the body). Many theorist investigators have 

 assumed that submergences of this magnitude were large enough to apply small 

 disturbance theory. Tuck (4) used twice the thickness as his largest submer- 

 gence. This wave breaking, however, is such a highly nonlinear phenomenon 

 that no perturbation theory can predict its occurrence. 



We note that for the 1.0-ft submergence the waves break for speeds between 

 about 2.5 and 5.5 ft/sec and that for lower speeds when the waves do not break, 

 the second-order theory agrees fairly well with measurements. 



Figure 18 is included to show that at even smaller submergences (b = 0.75 

 ft) the waves break down completely, leaving no regular waves behind the body 

 but only some kind of a "hydraulic jump." This has previously been observed 

 by Laitone (9) and by Parkin, Perry, and Wu (10). 



616 



