Ellis 



{a)o- = 0.266 



V = 39,4fl/sec 



(b)o- = 0.279 

 V = 39.6 ft/sec 



(C)<T 



0.239 

 85.34 tt/sec 



Fig. 1 - Cavitation on 1.5-caliber ogive 

 (10,000 frames/sec; 0.75X) 



was 1.0 microfarad in the case of Shutler and Mesler. Other things assumed 

 similar, this means that the period of the electrical discharge was fifty times 

 longer and therefore the hot arc was maintained during most of the bubble his- 

 tory. This conclusion is born out by the photographs which show the arc. It 

 does not seem reasonable to expect the jet to pass through the hot gas with any 

 vigor, and in fact it might try to move out to some radial distance and do peri- 

 pheral damage. However, a maintained arc should also be an excellent vortex 

 generator, and it is probably quite true that much damage producing cavitation, 

 especially in turbomachinery, has been vortex generated. 



One should be very careful not to assume that all damage is done by jets 

 and none by shock waves, however. It is a natural tendency to associate shock 

 waves with spherically symmetric collapse and then to discard the idea of dam- 

 age from shock waves when one finds that such collapse near a boundary is an 

 extremely unlikely event. The point to be emphasized is that shock waves can 

 arise from nonsymmetric impact of portions of the walls of a cavity with other 

 portions or with solid boundaries. In the former case the shock wave may still 



140 



