improvements in TVC inception were accomplished with a minimal decrease in the lift- 

 ing surface performance. In addition, the parent foil cavitation inception data 



scale with Reynolds number according to a ~ R ' and also agree well with the rela- 



2 ^ 



tion O = k C . A summary of the results for the optimum TVC delay concepts are 



given in Table 1. 



TABLE 1 - SUMMARY OF RESULTS FOR THE OPTIMUM TIP VORTEX 

 CAVITATION DELAY CONCEPTS 





Parent 



Roughness 

 600 U Pressure 

 and Suction 

 Side Tip 



Bulb 

 Small 



Passive Mass 



Inj ection 



2 



Active Mass 



Inj ection 



Q. = 4.54 2./m 



Lift Coefficient 

 Slope, m 



0.0523 



0.0530 



0.0513 



0.0531 



0.0523 



Am 



- 



1.3 percent* 



-2.0 percent 



1.5 percent* 



0* 



Drag Coefficient 

 Cp at Design C^ 



0.0159 



0.0159 



0.0170 



0.0161 



0.0144 



^S 



- 



0.0 percent* 



6. 9 percent 



1.3 percent* 



-9.4 percent 



Inception Curve 

 Constant K 



17.6 



4.8 



9.2 



9.8 



7.5 



Inception Speed 



Ratio U„/U Parent 

 3 P 



1.00 



1.91 



1.38 



1.34 



1.53 



*Within experimental accuracy. 



The flow visualization techniques employed in this study proved effective in 

 defining the detailed flow over the model hydrofoils and also provided the design 

 criteria for the various TVC delay concepts. The paint flow experiments indicated 

 that the flow over the hydrofoils was almost totally turbulent for the investigative 

 Reynolds number R ~ 5 x 10 . 



48 



