Jets and Shock Waves from Cavitation 



"1 



Fig. 2 - Spark bubble with a collapsing 

 jet within it. The thin line above the 

 bubble is the path of two tungsten 

 wires which carried the spark current 

 (100,000 frames/sec; 2.5X) 



^ 



^^*^- 



Fig. 3 - Pit left by single bubble 

 collapse (1 division is 0.004 inch) 



travel to the boundary and do damage. In the latter the damage would be done 

 by the impacting wall which may or may not be in the shape of a jet. Figure 4 

 shows a spark- generated bubble from unpublished work of Naude and Ellis which 

 collapses unsymmetrically and yet generates a shock wave. The origin of the 

 shock wave is obviously not at the solid surface and hence must be at a colliding 

 liquid-liquid interface. The lack of sharpness of the shock is due to the rela- 

 tively long exposure time of about 0.1 microsecond in this case. It should be 

 emphasized that the behavior of spark- generated bubbles in the absence of a 

 flow was not necessarily expected to duplicate conditions of flow- generated 

 cavitation. They were studied mainly because theoretical treatment was more 

 tractable than the general case of collapse in a flow field, but it was felt that 



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