Vassilopoulos and Mandel 



Fig. 68 - Model sections 



It is important to note, however, that in the important ship range of the frequency 

 parameter (0-1.5), the disagreement is minimum. Generally speaking, in the 

 case of the semicircular cylinders. Figs. 66 and 67, thefree-surface correction 

 factor, k^, as computed by Grim is less accurate than A, the amplitude ratio. 

 Also, for a given s, the discrepancies for both k^ and A increase with decreas- 

 ing beam to draft ratio. This is particularly noticeable for the low beam to 

 draft bulb-section (Model 5 of Fig. 68) as plotted in Fig. 70. This, in turn, 

 causes underestimations of heave and pitch damping and consequently forces the 

 strip theory to overestimate responses, particularly at resonance, as shown for 

 example by Model E. However, it has not yet'been possible to examine, in de- 

 tail, the overall effect these differences will have for a particular ship model in 

 a given condition. 



The most important reasons why efforts are now being made to incorporate 

 a version of Porter's work in our computer program are as follows: 



a. His solution of the theoretical problem is considered more exact and by 

 far the most general to date. 



b. His numerical scheme is much more stable although, at present, more 

 time-consuming than that of Grim. 



338 



