Motora and Koyama 



11. Y. Okumura and M. Sugiura, "On Wave Excitationless Ship Forms, Special 

 Reference to Three Dimensional Cases," Graduation Thesis, Tokyo Univ. 

 (1966) 



12. E. Tasaka, S. Motora, M. Kengaku, T. Ida, and M. Koyanagi, "An Experi- 

 mental Study of the Effectiveness of Anti- Pitching Tanks," Journal of Zosen 

 Kiokai, Vol. 177 (1965) 



13. S. Motora, 'T)iscussion to Gidding's paper," in "Fifth Symposium on Naval 

 Hydrodynamics," published by Office of Naval Research, ACR-112, p. 803, 

 available from Superintendent of Documents, U.S. Government Printing Of- 

 fice, $7.25, 1964 



DISCUSSION 



Capt. William R. Porter, USN 



Institute for Defense Analyses 



Arlington, Virginia 



I want to congratulate the authors for presenting a paper which includes not 

 only theoretical observations of interest, but also includes experimental evidence 

 that the observations in theory are reasonably valid in reality. I will confine my 

 technical remarks now to the case of two-dimensional bodies only. The points 

 on which I will comment are: 



1. Shiplike sections which do not generate waves when forced in vertical 

 oscillation at critical frequencies. 



2. Shiplike sections which are free of vertical excitation in waves at criti- 

 cal frequencies. 



3. Calculation of the hydrodynamic coefficients by exact, in lieu of approx- 

 imate, analysis. 



In their paper the authors report approximate techniques to calculate the 

 results for sections synthesized from simple shapes and which are free of ver- 

 tical excitation in waves. The same sections do not generate waves when forced 

 at critical vertical frequencies. In order to study such forms with shiplike sec- 

 tions, I have generated a number of sections within those mapped by the trans- 

 formation 



Z= ^ + E ^2i.l/^^ 



404 



