Oscillating-bladed Propellers 



FHV -.Flashing hub vortex 



e FS 



&■= o- J~ = 0°) 



Fig. 4b - Cavitation inception curves for 

 oscillating-bladed propeller, (9= 10 



other types of cavitation (except, of course, the hub-vortex cavitation, which in- 

 tegrates the behavior of all the blades) with an inverted effect of cp . 



Cavitation Patterns — The cavitation patterns (Figs. 5b through 7b and Fig. 

 10b) are more complicated than for the fixed-bladed propeller. First, according 

 to the longitude (p, the bubbles on the upper part of the back appear either amid 

 the section (type 2; cp -180"^), or near the leading edge (type 7; cp -- 0°). 



Second, there can exist a sheet cavitation along the face leading edge, even- 

 tually prolonged by a vortex (type 8). 



As in the case of the fixed-bladed propeller, the cavitation patterns are very 

 similar for ^ = 10^ and 6? = 15°. 



Influence of the Longitude cp — The influence of q? is less clear than in the 

 case of the fixed-bladed propeller. The cavitation near the hub (back or face) 

 seems to appear for about the same values of cp . As for the other types (bub- 

 bles, sheet vortex, tip vortex), they depend less upon (p than in the case of the 



1507 



