Jets and Shock Waves from Cavitation 



angle pointing downstream. At least in the no-flow case, theory indicates that if 

 a bubble is shaped like in the center figure, then a jet will develop. 



The theory for the flow situation is not yet complete, but it was felt that ob- 

 servations on an initially greater than hemispherical bubble in a flow would also 

 be helpful. Tungsten wires were extended into the stream from the minimum 

 pressure point of the circular foil, and the resultant sequence is shown in Fig. 6, 

 where the center and lower frames occur just before and just after collapse. In 

 this case, the shape in the center frame differs mainly from the no flow theory 

 in the development of an upturned tail on the downstream side. No explanation 

 has yet been advanced for this effect, although it seems to occur rather 



Fig. 5 - Initially hemispher- 

 ical spark bubble generated 

 at the minimum pressure 

 point of a circular-arc hy- 

 drofoil (a = 0.3; V = 30 ft/ 

 sec; 2.5X) 



Fig. 6 - A spark bubble 

 initially greater than 

 hemispherical (approx- 

 imately the same condi- 

 tions as in Fig. 5) 



143 



