3rd BUBBLE 

 PULSE 



Figure 1 . Pressure waves and bubble phenomena of underwater explosions. The upper part shows 

 a pressure-time plot, the lower, the position and size of the bubble for specific moments which 

 correspond to the curve above as indicated by the vertical lines. 



moving water carries it far beyond the point of pressure equilibrium. The outward 

 motion stops only after the gas pressure has fallen substantially below the ambient 

 pressure. Now the higher surrounding pressure reverses the motion. Again the flow 

 overshoots the equilibrium and when the bubble reaches its minimum size the gas is 

 recompressed to a pressure up to several hundred atmospheres. At this point we have 

 effectively a second explosion and the whole process is repeated. The bubble oscillates 

 in this way several times. 



In Fig. 1, the position and the size of the bubble is shown for a few specific 

 moments which correspond to the pressure-time curve as indicated above. The pressure- 

 time history reflects the low gas pressure during the phases where the bubble is large 

 and it shows the pressure pulses which are emitted from the bubble near its minimum. 



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