Charaatevistias of Ship Boundary Layers 



REPLY TO DISCUSSION 



L. Landweber 



University of Iowa 

 Iowa City^ Iowa 



Mr. Lackenby emphasizes the importance of boundary-layer 

 studies on tanker forms. Since the resistance of a tanker is mainly 

 viscous, and the power-wasting phenomena of bilge-vortex formation 

 and stern separation are viscous in origin, it is clear that such 

 studies are needed, if only to develop designs which avoid their 

 occurrence. 



For the particular tanker form to which Mr. Lackenby refers, 

 the wavemaking resistance was stated to be only 3 to 5 per cent of 

 the total. Our experience has been that the wave resistance of a 

 tanker model may be about 10 per cent of the total, and that if a 

 proper bow bulb is fitted, it may be reduced to about 6 per cent. 

 Since others have found that bulbs on tanker models reduce viscous, 

 rather than wave resistance, this indicates that the problem remains 

 to be resolved. 



I would like to thank Dr. Hogben for reminding us of his 

 Important 1964 boundary-layer paper, one of the very few available 

 studies of ship boundary layers. Explorations of this kind on other 

 ship forms are urgently needed to guide the development of methods 

 of computing ship boundary layers. 



475 



