Bindel 



Fig. 4a - Cavitation inception curves for 

 fixed-bladed propeller, - 10° 



The back cavitation is more developed when the blade is going down 

 (0 < tp < 180"'), especially the bubble cavitation near the hub, the tip vortex 

 cavitation depending only slightly on cp. Conversely, the face cavitation is 

 more developed when the blade is going up (180° < cp < 360°). ' -' '"<■ - ' 



Influence of the Inclination of the Shaft— The cavitation patterns are similar 

 for 6 = 10° and 15°, as can be seen from the comparison between Figs. 7a and 

 10a. This is the reason for which the pattern schemes relative to = 15° were 

 limited to one figure. 



As expected, the cavitation appears earlier for = 15° than for = 10°. 

 The difference is small for bubble cavitation in the upper part of the back (second 

 type) and for the sheet- vortex cavitation (third type). 



Oscillating- Bladed Propeller with Oscillation In- Phase 

 (7= ±3°; ^p = 0) 



According to Figs. 2b and 2c, an oscillation amplitude of ±3° could practi- 

 cally remove the cavitation near the hub and, on the other hand, strengthen the 



1506 



