390 



SECONDARY PRESSURE WAVES 



for a charge depth close to twent}^ feet, and its peak value was of the 

 order three to five times that for the level at greater depths. The exact 

 magnitude of the optimum pulse is uncertain for two reasons. First, 

 its occurrence is so critical to depth that it is not very reproducible, and 

 second, the observed pulse is diminished considerably by surface re- 



O-^. 



JHEORY 



^, 



TT 



600 

 500 



I 



-/■ 



/ 



/ 



y 



6 



.CJ 



UJUJ 

 OS- ^ 



Q.^-- O 



^2 



100 



80 60 40 



DEPTH (ft) 



20 



Fig. 9.11 Peak pressure and positive impulse, corrected lor surface and bot- 

 tom reflections, from 300 i)ound TNT charges fired in 100 feet of water. 



flection, for which a large, rather inaccurate correction was necessary in 

 these data. It has, however, been estimated that the corrected peak 

 pressure is at least one quarter of the shock wave pressure. The dura- 

 tion of the pulse, however, is relatively short, as impulse data (see the 

 following discussion) show no significant increase over values at greater 

 depths. The total energy flux is, in virtue of the high peak pressure, at 



