Motora and Koyama 



0.2 0.4 0.6 0.8 



Fig. 18 - Calculated heaving force of sphere type models 



5.2 A Prism in Longitudinal Wave 



In relation to the possibility of applying the strip method for three- 

 dimensional cases, it is important to know how a wave acts to a section of unit 

 length of a prism fixed in longitudinal wave train. 



This problem was treated by Okumura and Sugiura (11) for a prism of a 

 section shown in Fig. 13(b). A unit length of prism was cut off and kept free 

 from the main body and was supported by a rigid spring attached with linear 

 transformer as shown in Fig. 21, so that heaving force acting on this segment 

 was measured. 



Results are as shown in Fig. 22. In Fig. 23, heaving forces in beam seas 

 as well as longitudinal waves are compared with calculated values. Reasonable 

 agreement between them will suggest that the strip method will be applicable 

 for obtaining heaving force as well as pitching moment of ships in longitudinal 

 waves. Therefore, there will be a possibility to eliminate pitching moment of 

 ships by the same technique. 



6. COMPARISON WITH THE "WAVE-FREE 

 DISTRIBUTION" THEORY 



Bessho has given in his paper "wave-free distribution" (4), a group of two- 

 dimensional bodies which are wave-free as they heave in a free surface. They 

 are derived by the following procedure: 



Supposing m( t ) is a function which is regular at infinity and is vertically 

 skew-symmetry. Then a function 



f(t) = Km(t) + i -j^mCt) 



(10) 



398 



