LIFT COEFFICIENT Cl 



Figure 21 - Cavitation Inception as a Function of Lift Coefficient — Parent Foil 



the design condition, which tends to retard the tip vortex rollup process. Also pre- 

 sented in Figure 21 are the cavitation inception data for the various forms of sur- 

 face cavitation; i.e., leading edge pressure side, leading edge suction side, and 

 back bubble. As seen, TVC is generally the first form of cavitation to appear. 



TIP VORTEX CAVITATION DELAY CONCEPTS 

 Roughened Tip 



The use of artifical roughness for TVC delay is a relatively unexplored area. 

 Therefore, the work with this concept was primarily guided by a knowledge of the 

 detailed flow at the foil tip as deduced from the results of the paint flow visual- 

 ization efforts. In order to avoid substantial increases in drag, the roughness was 



30 



