



I 



I I I 



CAVITY THICKNESS TYPE AT FIG. 5, Cj) 



= (A, 1.054) 



CASE 1 



C ° M. 





(D, 1.315) 







— -«, 



— 1.0 



(B, 0.98) 



I 



1 





1 



> 



CASE 2 



1 



\ 



0.2 0.4 0.6 0.8 



r/R 



Figure 9 - Camber Distributions for Model 3770 



2.0 



1.0 



— 



I I I 



/ — ^__ CASE 1 



I 



CASE 2\ 

 I I 



- 



2 0.4 0.6 0.8 



r/R 



Figure 10 — Camber Distributions for Model 3870 



According to lifting-surface theory' 22 ', only a small correction is required to the cavity source 

 distribution for the infinite-cavity cascade; in the case of finite cavities the correction is comparatively 

 large. The efficiency of the lifting surface is also very close to the efficiency predicted by lifting- 

 line theory. The pitch and camber distributions computed by lifting surface theory are a little 

 smaller than those of lifting-line theory because of the effect of flow retardation. However, for the 

 supercavitating propeller designed with a short cavity, the corrections to the cascade cavity source, 

 pitch, and camber are quite large. 



It must be recognized in the old design of Propeller 3770, that angle is added to the angle of 

 attack of the two-dimensional supercavitating foil in the infinite medium as a lifting surface effect. 

 However, the increment of angle of attack is actually due to the cascade effect; the three-dimensional 

 effect is manifested as a decrement of angle of attack because of the effect of flow retardation. 



A comparison of the optimum pitch distribution obtained from Equation (7) and the pitch 

 distribution obtained from the normal condition r tan fi x = constant is shown in Figure 7. The 



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