EXPLOSION-GENERATED WATER WAVES 



Bernard LeM^haut€ 



Tetra Teah^ Inc. 

 Pasadena^ California 



I. INTRODUCTION: A review of the state of the art 



This paper reviews recent developments concerning water 

 waves generated by underwater explosions, with particular emphasis 

 on the wave generation mechanism. Analytic models for predicting 

 water waves from explosions in deep water are presented together 

 with methods for improving our understanding of the wave generation 

 mechanism. 



A submerged detonation almost instantaneously produces hot 

 gas or plasma v/ithin a limited volume. High temperatures and 

 pressures result in two disturbances of the ambient fluid: emission 

 of a shock wave traveling outward, which vaporizes a mass of water; 

 and radial motion of the fluid, so that the "bubble, " consisting of 

 explosive debris and water vapor, begins to expand. At the same 

 time, if undisturbed by bounding surfaces, it begins to rise due to 

 its buoyancy. 



During the expansion phase, pressure within the bubble falls 

 considerably below the ambient hydrostatic pressure, owing to its 

 outward momentum acquired by the water. The motion then re- 

 verses; the bubble contracts under hydrostatic pressure, [acquiring 

 inward momentum and adiabatically compressing the central gas 

 volume to a second -- but lower -- pressure.] Upon reaching Its 

 minimum diameter, several phenomena may occur: energy is radi- 

 ated by the emission of a second shock wave; if near the free surface, 

 the contracted bubble will not be spherical but may evert, the bottom 

 rushing up and passing through the top; lastly, the surface of the 

 contracting bubble is extremely unstable --it may break up irregu- 

 larly, forming a spray within the bubble. 



The bubble may lose enough energy through repetitive expan- 

 sions and contractions so that it collapses entirely, leaving a mass 

 of turbulent warm water and explosion debris, and no waves of conse- 

 quence will be generated. This case is typical for large, deeply 

 submerged detonations, and will not be further discussed here. 



For shallower explosions, the nature of ensuing surface 



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