56 Lecture 3 
30 
Theory for7 S| 
501b Charges 
— 
= a 5F 
@ ae Measured 
SFG oF / octave a 
& ° differences 
= x 
Qa 
2 4 6 8100 2 4 6 81000 2 4 6 810000 
Frequency (c/s) 
Fig. 3.3. Differences from a 1-lb charge. 
1. There is a Riemann broadening and sharpening of the shock pulse; the 
latter keeps the viscous losses at the shock front at a high level. 
2. Reflection at the sea surface is imperfect due to Cavitation. 
3. Some of the lost energy may be reradiated eventually; due, for example, 
to water droplets falling back into the sea. 
4. At small glancing angles a strong shock wave suffers an irregular type 
of reflection at the sea surface, which may be compared or contrasted 
with Mach reflection. 
5. Due to migration under gravity the bubble pulses may be radiated from 
a reduced depth. ; 
Most of these points are usually unimportant but it is necessary to watch 
them. 
