Jets and Shock Waves from Cavitation 



Fig. 13 - Acoustic cavitation at 18 kilocycles 

 generated by a ceramic ring method. Note the 

 shock waves from small collapsed bubbles away 

 from any interface. (Photographic details are 

 the same as in Fig. 12.) 



The equipment recently set up at Caltech to continue single -bubble -collapse 

 studies at higher and more completely controlled pressures is shown in Fig. 14. 

 It consists of a 4-inch-diameter Lucite cylinder about 5 feet long mounted on an 

 electromagnetic shaker of 5 -kilowatt power rating. The relatively high rating 

 permits easy degassing of the water by vertical sinusoidal motion of the entire 

 column without the necessity of operating at discrete resonant frequencies of the 

 apparatus. To grow larger cavities from small gas nuclei a large downward ac- 

 celeration of the tube (about 30 g) is obtained by discharging a capacitor through 

 the energizing coil of the shaker by firing an ignitron rectifier. Since the igni- 

 tron passes current in one direction only, a half sine wave of current results, 



Fig. 14 - Electromagnetic shaker and 

 vertical liquid column. The bubble 

 nucleus generator is close to the bot- 

 tom of the tube. 



149 



