Yim 



37. Yim, B., "On Ships with Zero and Small Wave Resistance," Proc. of the In- 

 ternational Seminar on Theoretical Wave Resistance, The University of 

 Michigan, 1963. 



38. Yim, B., "The Higher Order Effect on the Waves of Bulbous Ships," HYDRO- 

 NAUTICS, Incorporated Technical Report 117-5, 1964. 



THE SHIP BULB 



Ata Nutku 



Technical University 



Istanbul, Turkey 



The merits of the ship bulb as a resistance reducing mean has first been de- 

 tected by Admiral D. W. Taylor. However, a great amount of testing has since 

 been carried out to utilize it as an improving medium of ship form. The testing 

 has been confined to minor changes on its size and form, and no attempt has 

 been made towards a scrutiny on its basic concept or characteristic function. 



As a matter of fact, the bulb today stands as we have inherited it from our 

 forefathers who designed and used it for ramming the enemy ships during ac- 

 tion. The original form of the bulb has been conservatively retained with only 

 minor changes, which has satisfied its experimenters within the limits of 2 per- 

 cent to 5 percent gain in total resistance of a ship. Some of the explanations for 

 the action of the bulb may be summarized as: 



(a) lowering centre of pressure zone at bow, 



(b) displacing the bow wave to forward, consequently changing the phase of 

 the wave system as to their order of synchronization, and 



(c) causing a suction on the surface wave phenomena. 



All the above will consequently cause change of flow pattern at bow. 



The section of the bulb has attracted my attention from the observations 

 made on the behaviour of a submerged circular streamlined body towed near the 

 surface at different depths, and from the analysis of the results of its resistance 

 and trimming moments. The purpose of these tests, conducted in the years 

 1956-57 has been purely academic, parallel to Wigley's and Gawn's experiments 

 with fish form bodies. 



I acknowledge the help and directives given by Prof. Dr. Giinther Kempf, 

 who was then a visiting professor in t.T.U. 



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