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and his associates in England. In this country, theoretical 

 work was started by C. Herring (Division 6, N.D.R.C. ) and 

 is being carried on at the David Taylor Model Basin (in par- 

 ticular by Captain W. P, Roop, E. H. Kennard, 0. E. Hudson) 

 and by the W.Y.U.Qroup of the A.M. P. at the request of the 

 Model Basin and of the Bureau of Ordnance; considerable experi- 

 mental research is being done at the Underwater Sound Labora- 

 tory of Division 8, N.D.R.C 



Taylor [3] and others have determined the upward motion 

 of the bubble under the buoyant force of gravity, a motion 

 taking place in jerks. Herring [4] and others have studied 

 the manner in which rigid walls attract the bubble, assuming 

 that the bubble is rather far from the wall. Shiffraan [5] 

 has developed an improved method which permits numerical 

 analysis of the motion when the bubble is close to the wall, 

 and even when it touches the wall. The influence of non- 

 rigid walls and the repulsive effect of the free surface of 

 the water on the bubble have also been studied. Much of the 

 material is condensed and supplemented in the comprehensive 

 work by Kennard[6]. 



A very Important aspect of the problem is concerned 

 with plastic-elastic deformations of the target in inter- 

 action with the motion of the water. The process of damage 

 can be understood only by a careful analysis of this inter- 

 action. Extended research by J. G . Kirkwood [7] has estab- 

 lished that the damage to a structure depends on the ratio of 

 the duration time of the incoming pressure pulse to tlie "time 

 constant" of the structure, i.e., the span of time during 

 which the structure is "receptive" to the impinging pressure 

 effects. If this ratio is small, the liTrpulse is the more 

 important factor for damage, while if it is large, the peak 

 pressure is more iinportant. 



Another problem that should be mentioned is that of 



