(c) . The 600-micron grain size appears to be the most effective; e.g., for 

 angles of attack close to design, 0.28 £ C ^ 0.36, the 600-inicron size produced sub- 

 stantially larger values of U„/U as compared to the other grain sizes. 



p P 



The roughness suction side surface cavitation inception data are given in Figure 



25 for the standard roughness pattern. These data were recorded for the first ap- 

 pearance of cavitation on the distributed roughness and were generally associated 

 with a localized nonuniformity which resulted during the application of the rough- 

 ness. A more uniform application of the roughness should result in lower as for all 

 the grain sizes. For the foil suction side tip, the trends are as expected and show 

 that the larger grain sizes result in higher a values or lower cavitation inception 



-0.3 



-0.2 



-0.1 



0.1 0.2 

 LIFT COEFFICIENT C, 



Figure 25 - Surface Cavitation Inception as a Function of Lift 



Coefficient for Varying Roughness Grain 



Size — Standard Roughness Pattern 



35 



