Some Hydrodynamic Aspects of Ship Maneuverability 



NORRBIN (L T = 17.5) 



THEORY (HU) L, T = 20 



• MOTORA AND FUJINO oj'~ 0.15 (L/T = 18 7) 



-♦ cj= 

 -A tj'= 10 



1.. 



EEUWEN (L T = 17 5) 



2 0.3 



FROUDE NUMBER V / V^ 



Fig. 8 - Comparison of theoretical drift 

 moment with various experiments (an 

 asterisk denotes experiments with bare 

 hull; in all other cases the data is for 

 base hull with rudder) 



60 (Block .60) hull of length approximately 2 meters; Norrbin tested a cargo 

 liner model of length 5.5 meters, and at zero Froude number his results were 

 obtained with a geosim double -body model of length 2.7 meters. One set of the 

 results of van Leeuwen (denoted by *) are for the bare hull alone, while the re- 

 maining experiments are for the bare hull with rudder. The experiments of 

 Norrbin, and one set of van Leeuwen 's data, were obtained from steady towing 

 tests with a static drift angle; the remaining tests of van Leeuwen and the re- 

 sults of Motora and Fujino are based upon the analysis of slow oscillatory drift- 

 ing motions at the values of the nondimensional frequency parameter co' = oj(L/g)^''^ 

 shown. 



It should be noted that the free surface can give rise to a steady side force 

 without the existence of circulation, so that thickness effects as well as the an- 

 gle of attack must be considered, in contrast to the analogous aerodynamic situ- 

 ation. These can be analyzed in much the same manner as the wave resistance. 

 A cOHvenient starting place for such a study is with Kochin's equations for the 



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