Application of Wavemaking Resistance Theory 



.20 



.25 



.30 



.35 



Fig. 7 - Comparison of theoretical 

 C^ curves of Models B and C 



figure also indicates that a good vertical displacement- volume distribution at 

 low Froude numbers may not necessarily be good at higher Froude numbers. 



2 



In Fig. 8, C^ curves are given for three cases with M(<f,0 = ^, 4/3 cf , and 

 7/3 ^^ , respectively. To a first approximation, all three cases have the same 

 displacement volume. At low Froude numbers, the differences between the 

 three curves are amazingly large, mainly due to changes in angle of entrance. 

 It is also interesting to note that in the case of M(^, O = 7/3^^, the last hump is 

 much less pronounced than the preceding ones. 



REDUCTION OF VISCOUS DRAG 



The viscous drag constitutes a major portion of the total resistance of a 

 ship. A great potential, therefore, exists for reducing total resistance by de- 

 creasing the viscous drag, which is mainly a function of wetted surface and 

 Reynolds number. However, if not designed properly, the hull form can produce 

 large eddies, resulting in a large form drag. Therefore, to reduce the viscous 

 drag, we have to reduce both the wetted surface and the form factor. 



We know how to shape a hull to keep down viscous drag for a deeply sub- 

 merged body, but such information cannot be directly applied to designing a ship 

 hull subject to free- surface effects. In ship design, the principal dimensions 



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