Wave Analysis Techniques to Achieve Bow-Wave Reduction 



appearance of the bow waves on the models with and without a bulb as compared 

 in Fig. 12. Although the photographs are only a poor reproduction of the flow 

 conditions actually observed during the tests, and there are certain extraneous 

 features such as irrelevant foam patches on the free surface (foreground of Fig. 

 12(a)), it should be evident that the bow wave of the bulbless model has a broken 

 crest and produces violently turbulent motion, while the bulbous model exhibits 

 a fairly smooth flow. It is quite conceivable that in face of such highly nonlinear 

 (and in fact nonpotential) flow phenomena the present linearized method of wave 

 analysis would yield inaccurate results and generally tend to underestimate the 

 "actual" wave-making resistance. 



In spite of such possible shortcomings of the present method of analysis it 

 was attempted to derive some practical results relevant to the optimization 

 problem. To this end the theoretical effect of changing bulb size and location 



(a) BOW WAVE OF BULBLESS MODEL 1877 AT 2.065 m/s 



(b) BOW WAVE OF BULBOUS MODEL 1877-1 AT 2.057 m/s 



Fig. 12 - Comparison of bow waves with and with- 

 out bulb at the operating speed in the ballast con- 

 dition: (a) bow wave of bulbless model 1877 at 

 2.065 m/sec and (b) bow wave of bulbous model 

 1877-1 at 2.057 m/sec 



761 



