AN ATTEMPTED APPLICATION OF 

 WAVE ANALYSIS TECHNIQUES TO 

 ACHIEVE BOW-WAVE REDUCTION 



S. D. Sharma 



Hamburgische Schiffbau- Versuchsanstalt 



Hamburg, Germany 



ABSTRACT 



Two longitudinal -cut methods of analyzing the wave systenn of a ship 

 model, originally proposed by the author in 1963, have been numerically 

 and experimentally verified. It has been found that the free wave spec- 

 trum of a given model can be derived with fair accuracy fronn measure- 

 ments of wave height or slope along a single track parallel to the direc- 

 tion of nnotion, provided suitable truncation corrections are applied to 

 account for the asymptotic behaviour of the wave profile behind the 

 model. A concrete exannple shows that such empirical information on 

 the wave making characteristics of a nnain-huU form can be used as a 

 basis for the theoretical design of an additive bow bulb which would 

 achieve optimum wave cancellation and thus indirectly reduce ship re- 

 sistance and improve performance. 



PART I 



INTRODUCTION. 



This paper presents the first results of a research project initiated about 

 a year ago with a view to devising a systematic method for the design and ap- 

 propriate dimensioning of bulbous bows. It is generally recognized that the 

 beneficial action of the bow bulb in reducing ship resistance and thereby im- 

 proving performance results primarily from an attenuation of the bov/ wave 

 system which is usually accompanied by a reduction of wave making resistance. 

 Even in such cases, with fuller ships for example, where there is good reason 

 to believe that the bulb tends to reduce the viscous rather than wave resistance 

 by smoothening the flow around the forebody, the wave reduction can be used as 

 a good practical criterion for bulb efficiency, since it is an empirical fact that 

 optimum designs of least total resistance generally display the least surface 

 disturbance in the vicinity of the bow. Therefore, it seems to be a sound work- 

 ing principle to try to match the bow wave system of the main hull against that 

 of an additive bulb. 



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