Salvesen 



4 5 



SPEED U , ft/sec 



Fig. 13 - Wave resistances 

 for 1.25-ft submergence 



show that the rather large discrepancy at higher speeds between the theory pre- 

 sented here and the experiment is indeed due to the inaccurate body representa- 

 tion. 



The wave resistance curve obtained from horizontal drag measurements 

 seems to be rather high at the lower speeds, which seems to indicate that the 

 viscous drag is not the same at 4.5-ft and 1.25-ft submergence but that it in- 

 creases as the body gets closer to the free surface. This is most likely due to 

 an increase in the velocity of the fluid particles next to the body as a result of 

 the free surface. Furthermore, this proves how extremely difficult it is to de- 

 termine the exact wave resistance from drag force measurements. The author, 

 therefore, strongly believes that we should not compare wave resistance curves 

 but rather wave profiles when checking the accuracy of theoretical work. 



Figures 14 and 15 show the wave profiles and the wave resistance curves 

 for 1.50-ft submergence, and as expected the agreement is even better at this 

 larger submergence. 



614 



