1261 
TABLE I 
Medium Incident Pulse Pressure-Time Curve at Wall Fig. 
Shape Peak Pressure Impulse / Acoustic Impulse 
“Catm) 3% Numerical Analytical 
Water Linear 300 LeLO 0.98 0.98 2 
( Y=7.15) 
' Linear 1800 1.60 0.92 0.92 Za 
Expon. 300 aL Al{e) 0.97 a 3, 
Expone 1800 ak ~60 0.90 haa fore ona 3a 
Air Linear 1.50 1.50 1.04 1.04 4 
( y¥=1.40) 
Here : is the ratio of the greater to the lesser effective 
pressure on the two sides of the incident shock. In this 
table "impulse" means the time-integral of the overpressure 
at the wall. In computation of impulse the duration of an 
exponential pulse was arbitrarily taken to *. the time re- 
quired to fall to an overpressure of three atmospheres. The 
impulse is normalized by dividing it by the “acoustic impulse", 
AO GR, (2 Jr: dt, where Ps is the value the overpressure would 
have at the position of the wall, if the wall were absent 
and all parts of the incident wave moved forward with the 
velocity of sound in undisturbed fluid. In fig. 2, 2a, and 
4, the points obtained by the numerical method are circled, 
and the curve calculated by the analytical method is drawn 
in. The agreement is seen to be good. Fig. 4 provides a 
test not only of the analytical method, but also of the 
adiabatic assumption mentioned in par. 7, inasmuch as the 
circled points in this fig. were calculated by Chandrasekhar 
