437 
curve of the shock wave, The intensity and shape of the wave are determined 
by the dissipation parameter A and the spread parameter xX. These quanti- 
ties take on particularly simple forms at large distances from the charges, 
R/a,> > { - An examination of their asymptotic forms permits a clearer 
grasp of the physical characteristics of the pressure wave than is to be ob- 
tained from the more exact but more complicated formulae of the preceding 
discussion, 
The propagation equation has been written in the form 
QER,t) = 4 (a,/RI2, e118 
6=8yY, be tot : (52h) 
where t, is the time at which the wave front arrives at point ff » and where 
the dissipation parameter XA and spread parameter Y are given by Eqs 5,21 
and 5.23. At distances at which 2 (R Ai a) can be represented by its acous- 
tical approximation b/p >» Eqe 5-24 yields for the pressure, 
p= 2/R) F, areae , 
p = Pel, , 8 = 8, V(R/a,) | (6.21) 
c) 
Xx = AlP/e,) , 
where ©, is the density of water at zero pressure. For most explosives, 
p/, fo is an entirely adequate approximation tof2 at distances exceeding 
twenty-five charge radii, 
At large distances from the charges, R/a o?7! , the wave propa- 
gates with nearly acoustic velocity c,), and a sufficient approximation for 
the particle velocity u (cf. Eqe 3.23) is 
7G.) i 
. CoE * OR 
50 
