l^tiv 



Bindel 



Flashing hub vortex 

 Flashing tip vortex 



r= 0- 



Fig. 9a - Cavitation inception curves for 

 fixed -blade d propeller, 6-15° 



CONCLUSIONS 



1. The experiments carried out on a propeller model in inclined flow 

 confirm, when the blades are fixed, the calculated influence of the longitude 

 on the inception and development of cavitation, especially as regards the cavi- 

 tation near the hub (bubbles on the back, sheet on the face leading edge). 



2. For this propeller, the oscillation of the blades can delay the cavita- 

 tion near the hub (back cavitation for the oscillation in phase with the incidence, 

 face cavitation for the oscillation in advance of 30°), but the cavitation far from 

 the hub is strengthened and even new types of cavitation can appear. 



3. K the results obtained with this propeller do not seem as a whole very 

 promising, a valuable conclusion regarding the oscillating-bladed propellers 

 cannot be drawn without further experiments, especially with large-pitch 

 propellers. 



4. The influence of the amplitude and of the phase of the oscillation should 

 also be investigated more thoroughly. For example, when two types of cavitation 



1514 



