409 



SUCTION SIDE 



PRESSURE SIDE 



PROPELLER B 



Re|^:0.51 xlO"- 



RCf^: 0.66x10 



FIGURE 11. 

 30% Slip. 



Paint patterns at 



radius of the propeller. Such a critical radius 

 can also be observed from the paint pattern of 

 Sasajima (1975) and of Meyne (1972). This critical 

 radius turned out to be very important for cavita- 

 tion inception and could be discerned in all cases. 

 No photographs are shown because of the bad contrast 

 of the monochrome prints. (Figure 16). 



On propeller B at 60^ slip a separation bubble 

 at the leading edge was observed, connected with a 



stagnation region near the tip on the suction side, 

 which indicated the position of the tip vortex. In 

 the direction of the hub the laminar separation 

 hubhle extended exactly until the critical radius. 

 This lead us to the hypothesis that laminar sepa- 

 ration near the leading edge was the cause of the 

 discontinuous character of the paint streaks at the 

 critical radius. To verify the hypothesis of laminar 

 separation at the critical radius, boundary layer 



