302 



MOTION OF THE GAS SPHERE 



The observed rises were systematically somewhat less than the cal- 

 culated ones, and close to the surface were increasingly smaller, be- 

 coming negative (i.e., a downward displacement) when the charge was 

 a few feet below the surface. This phenomenon is shown in Fig. 8.9, 

 which is a plot of similar data obtained at Woods Hole for 250 gm. tetryl 

 charges (2). Migrations at the end of both the first and second cycles 

 are shown and the solid line is the curve predicted by Eq. (8.32) for this 



o 



UJ 



C/) 



o 

 < 

 q: 



OIL SURFACE (AT ZERO PRESSURE) 



TIME (msec) 



Fig. 8.10 Motion of spark generated bubbles for Zo' = 1.0 compared with 

 theory. Solid circles are measured radii, open circles measured rise of the 



center. 



charge and weight. The decreased and reversed migrations near the 

 surface and bottom are accounted for by the surface attraction and 

 bottom reflection and are further considered in section 8.11. 



D. Model experiments. A more detailed comparison of Taylor's 

 theory with experiment than has been obtained with explosive charges 

 was made by Taylor and Davies (109) in a very beautiful series of model 

 experiments, in which gas bubbles produced by electrical discharges in 

 water or oil were photographed. The bubbles so obtained involved 

 energies of the order 1/40 calory and so correspond to roughly 2.10~^ 

 pounds of TNT. The bubbles had a maximum radius of a few inches, 

 and to simulate larger scale explosions it was necessary to reduce the 



