Figure 7 2. Shallow Explosion with Gas Blow-Out. Charge: 4200 lbs TNT. Depth: 2.1 charge radi 



be one reason why this method did not always give consistent results. There is a 

 theory by Keller and Kolodner [17] on this spray formation. A quantitative correla- 

 tion of their calculations with experimental evidence has not been made. 



The Water Column 



Fig. 12 illustrates the development of the water column from a very shallow 

 explosion. (Test made by Young and Willey, NOL.) The gaseous reaction products of 

 the explosion blow out into the atmosphere and form a dark cloud of smoke and 

 water. The column below is practically cylindrical and it is hollow inside. 



Rosenbaum and Snay [18] have theoretically studied the growth of such a 

 water column. They calculated the fluid motion which is produced by an expanding 

 cylindrical piston. Of course, this analysis cannot explain why this water column has 

 a cylindrical shape. This has been studied by Hudson (see his discussion at the end of 

 the paper). 



Fig. 13 shows a somewhat deeper * explosion. There is very little or no gas 



* The tests discussed here were not carried out with the same charge weight. There- 

 fore, the terms "shallow depth" or "great depth" must be understood as relative measures that 

 account not only for the actual depth of the explosions, but also for the weight of the charge. 

 A suitable way of doing this is to measure depth either in charge radii or in maximum bubble 

 radii. This parameter assures geometric scaling and the qualitative appearance of the surface 

 phenomena depends largely on it. Some quantitative effects, in particular the height of the 

 column, depend on a further parameter which is essentially the absolute weight of the charge. 

 This also holds for phenomena induced by the gravity migration of the bubble, for instance 

 the formation of the plumes. 



338 



