1189 
THE EFFECT OF STRATIFICATION OF SEA-WATER 
ON THE PROPAGATION OF AN EXPLOSION PULSE. 
H. N. V, Temperle 
. 
March 1944 
* * * * * * * ” 
Summary 
It is possible that the propagation of the pressure-pulse from an 
underwater explosion may be affected If the velocity of sound is different at 
different depths of water, The suggestlon by Professor Taylor that energy 
may be concentrated near the surface by a layer of fresh water lying over 
salt water, and that shock damage may thus be caused to ships at abnormally 
great distances, is exanined mathenatically (using linear sound theory). 
It appears that the energy flow per unit area might be increased by a factor 
of the order of three if the top ten feet of water were fresh instead of salt 
provided that the explosion occurs in, or within a few feet of, this layer. 
The effect of temperature variations is concluded to be too small to produce 
an appreciable effect. The extent to which these conclusions are affected 
by the departures of explosion pulses from ordinary acoustic theory is 
uncertain. 
Introduction. 
It has been suggested that the propagation of the pressure pulse from 
an underwater explosion may be naterially affected by the fact that, due to 
variations in temperature and salinity, the velocity of sound is different in 
different places. In particular, certain cases of shock damage to ships at 
unexpectedly targe distances of. the order of 1,000 yards might be accounted 
for by a concentration of energy by some such mechanism (1). An investigation 
of this point, following up suggestions nade by Professor G 1, Taylor has 
been nade. In order to make the mathematics nanageable, it has been necessary 
to use ordinary sound theory, to neglect both the variation in the velocity 
of sound with pressure and the cavitation phenomena which occur when an 
explosion pulse is reflected at a free surface, This means that we cannot 
hope to obtain more than a semi-quantitative picture of what takes place, but 
the indications secm to be that isolated cases of shock damage at abnormally 
great distances can be accounted for in this way. 
The Physical Hechanism. 
Although one can think of a numter of ways In which a concentration 
of energy might be caused, practical considerations seem to narrow down the 
field of choice, One might imagine a section of coast or sea—bottom acting 
as a concave mirror, or a large body of water, slightly different from its 
surroundings, acting like a converging lens.(2). Such possibilities cannot 
be ruled out, but it is almost impossible to form an estimate of their 
probability or importance. We consider here a phenomenon that is definitely 
known to be appreciable, the refraction of sound by stratified saa-water. 
A little consideration shows that the general effect of refraction is to 
concentrate the flow of energy into those reafons where the velocity of sound 
is least. We consider, therefore, the case of a "slow" layer of water lying 
ADOVE weoaece 
