407 



7r'0 95 

 0,91 

 0,81 

 72 

 62 

 O 53 

 O 43 



7r=0 95 

 9 

 08 

 0,7 

 06 

 0,5 

 0,31 



FIGURE 9. Calculated pressure distribution on the 

 suction side at 30% slip. 



and loading, which occur due to the non-planar 

 surface of the propeller blades are taken into 

 account by a correction factor [Morgan et al. (1968)] 

 This makes it possible to apply conformal mapping 

 to calculate the pressure distribution. An approx- 

 imation of the original theory of Theodorsen (19 32), 

 known as Goldstein's third approximation [Goldstein 

 (1948) ] was used. The determination of the "effec- 

 tive geometry" was done using a camber line, derived 

 from the calculated induced velocities of the lifting 

 surface calculation. This can be done because the 

 problem is linearized. The calculated induced 

 camberline and the geometrical thickness distribution 

 were combined in the NACA-manner to obtain the 

 geometiry of the effective profile. The pressure 

 distribution on the propeller section was then cal- 

 culated using the induced angle of attack from the 



lifting surface calculation. The lift coefficient, 

 which is found from the lifting surface calculation, 

 is maintained using the method of Pinkerton (1934). 

 This is necessary because the potential flow lift 

 coefficient of the effective profile is slightly 

 lower at inner radii, where the sections become 

 thicker. The differences are of the order of 0.02. 

 In Figures 9 and 10 the calculated pressure 

 distributions at the suction side are given for 

 propellers A, B, and C. 



4 . RESULTS OF PAINT TESTS 



In Figure 11 the paint patterns are shown for pro- 

 pellers A, B, and C at 30^ slip and at Reynolds 

 numbers typical for testing behind 12 meter models. 



