2.1 



2.0 I — 

 1.9 



3 





>, 





3 



1 7 



O 





1- 





< 





DC 



1.6 



O 





lU 





lU 









M 



1.b 



Z 





o 





o. 



14 



lU 





o 





z 







1.3 





1.2 



1.1 



Rp = 5 (10)® 



O PMI 1 



C^ PMI 2 



D PMI 2 WITH ROUGHNESS- 

 600 n, 12.7 mm STRIP 

 PRESSURE SIDE TIP 



0.20 



0.24 



0.28 0.36 0.32 



LIFT COEFFICIENT C, 



0.40 



0.44 



0.48 



Figure 32 - Tip Vortex Cavitation Inception Speed Ratio as a Function of 

 Lift Coefficient for the Passive Mass Injection Foil 



channel size. The optimum PMI channel size would have to be determined on a model 

 with sufficient tip thickness. The data for the PMI 2 with roughness show sub- 

 stantial increases in the TVC inception speed as compared to the PMI 2 without 

 roughness. Comparsion of the data for PMI 2 with roughness (Figure 32) and the 

 corresponding roughness alone (Figure 26 diamond symbols) show that the individual 

 performance gains are approximately additive. 



Active Mass Injected Tip 



As discussed previously, the principles governing the Active Mass Injected 

 (AMI) and PMI tips are similar, the only difference being that the AMI mass flow 

 rates into the vortex core are augmented by an external energy source. The end of 

 the AMI tube was located in the tip of the foil suction side at the observed 



45 



