Dynamics of Hydrofoils as Applied to Naval Propellers 



case B: A propeller for cargo boats, with a low value of expanded blade area 

 ratio and a high value of thrust coefficient (Table 6), constructed, as case 

 A , with identical design data and identical radial thickness distribution, but 

 according to the three solutions: 



E.1031 mean line a = l lift by camber alone, 



E.1066 mean line a = 0.8 lift by camber and by angle of attack associ- 

 ated with the mean line, 



E.997 mean line NASA 65 lift by camber alone. 



case C: 



E.997 as above (basic model) •. . -. .. , ..rij ^ !,• 



E.998 camber reduced by 50% with reference to the basic model, 



E.999 camber increased by 50% with reference to the basic model. 



The mean line NASA 65 was adopted for each of the three models, and the thick- 

 ness distribution and chord length were identical in each case. 



The aim of investigations A and s was to check the effect of the mean line 

 and of the blade width; the aim of c was to emphasize the effect of the camber. 

 The hydrodynamic calculation for cases A and B was carried out on the basis of 

 the vortex theory, involving, in particular: 



optimum circulation distribution; 



ideal efficiency as illustrated by Shultz in the DTMB Report 1148; 



Goldstein factors reported by Tachmindji in the DTMB Report 1141; 



theoretical lift coefficients and pressure coefficients on the suction 

 side as for the numerical expressions and coefficients referred to in 

 Sees. 2.1 and 2.2; 



real fluid reduction coefficient 0.75 for all mean lines; 



lift coefficient for angel of attack c^^ = 0.1a°; 



corrections for camber and angle of attack according to Ludwieg- 

 Ginzel. 



The thickness distribution NASA 16 was adopted for all the models. Theo- 

 retical performances for models E.998 and E.999 were determined by means of 

 a "reverse calculation"; this allows an evaluation of the hydrodynamic charac- 

 teristics to be made for any desired advance coefficient (in this case that of the 

 basic model E.997) when the geometry of the propeller is given in its entirety. 



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