l..^. 





1 1 1 1 1 



R, = 5 (10)^ 



1 



2.0 



— 



c 











— — PARENT TVC 



dJ" 



1.8 



- 



SURFACE CAV 



1 " 







Q LARGE 

 □ SMALL 



/ '^ 



1.6 



_ 



o- rt 







A SMALL WITH ROUGHNESS- / 



>^ 



b 





600 p, 12.7 mm STRIP / 



* o .^ / 



X 1-4 



— 



PRESSURE SIDE TIP / 



" f^y J 



UJ 



a 





/ 



^ / / 



2 



Z 1-2 



_ 



/ 



/ / / _ 



1 





/ 



d / y 



< ..0 



> 



- 



/? 



p4 



< 







/ Vi-/ 



f 



" 0.8 



— 





/ IP 



/ » __ 









"y^ SURFACE 



0.6 



'— 



^^x>ocua._CL 



-<K>0--^T2 



0.4 



^ 





/yA 



CAVITATION - 



0.2 



u- 





/yO^ 



- 







1 1 1 ^.^^^"^ 1 1 



1 



-0.3 



0.2 



0.4 



0.5 



LIFT COEFFICIENT C, 



Figure 29 - Cavitation Inception as a Function of Lift 

 Coefficient — Bulbous Tip Foils 



A bulb with roughness was also evaluated. For this experiment, 600-micron 

 roughness was applied to the small bulb pressure side tip over the area 0.5 in. 

 (0.013 m) inboard from the bulb tip. As seen in Figure 29, this configuration 

 resulted in substantial improvement in TVC performance as compared to the bulb with- 

 out roughness. These data indicate that the roughness is also effective in delaying 

 TVC for configurations with unloaded tips. 



The bulb data are also presented. Figure 30, to show the relative increase in 

 TVC inception speed over a range of C . As seen, the larger bulb gives increased 

 TVC inception speeds of from 10-15 percent higher than the smaller bulb. 



41 



