Wave Analysis Techniques to Achieve Bow-Wave Reduction 



0.8 r 



Fig. 10 - Amplitude spectrum of a 

 cargo ship model at ballast draft 

 for 7o = 7.27 or F^ = 0.262 



exhibits regular oscillations arising from interference between bow and stern 

 waves typical of any singularity distribution (see Fig. 3) in the linearized theory, 

 while the differential bulb spectrum is a fairly monotonic curve characteristic 

 of a concentrated point disturbance (see Fig. 1), The irregular high frequency 

 fluctuations visible in the bulb amplitude function could be attributed to experi- 

 mental error, while the somewhat more regular low frequency oscillations could 

 result from nonlinear interaction between the main hull and bulb spectra. 



Before passing on to the bulb optimization problem it may be useful to refer 

 to the total resistance curves reproduced in Fig. 11. It will be seen that the ef- 

 fect of the bulb is by no means spectacular but that there is a definite reduction 

 of total resistance over the entire speed range tested, amounting to about 12 

 percent at the ballast draft and 2 percent at the load draft at the respective de- 

 sign speeds. (The corresponding figures for the full-size ship would be pre- 

 sumably somewhat more favorable.) However, in view of the modest size of the 

 bulb (less than 1 percent of the main hull volume, see Table 9) this seems to be 



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