1069 
MEASUREMENT OF THE SHOCK-WAVE VELOCITY IN AIR 
ABOVE A WATER SURFACE, DUE TC THE DETONATION 
OF A SUBMERGED CHARGE 
D. Croney and R, D. Davies 
Road Research Laboratory, 
London 
April 1944 
* * * * * » * » 
Summary. 
The velocities of the shock wave and water surface due to the detonation of submerged 
Yeoz. Cylindrical charges of C,2., have been obtained over the first 3 ft. above the water 
surface from a determination with a rotating arum camera of the extinction times of a row of 
acetylene jots, situated in air vertically above the cnarge. 
With the charge at a depth of 2 inches, the water surface and shock-wave velocities 
were indistingulshable vertically above the charge, tne water surface velocity falling from 
about 4,500 ft,/sscond at 3 inches, to about 2,600 ft./second at 3 ft. above the surface, 
For charge deoths of 4 incnes and 8 inches, shock-wave velocities at 3 Inches from the 
water surface were 1,900 and 1,450 ft./second respectively (axis vertical and horizontal), 
corressonding velocities at 3 ft. were 1,500 and 1,200 ft./secona (axis vertical} ano 1,250 and 
1,150 ft./secona rescectively (axis horizontal). 
water—surface velocities fcr the 4 inches ana 8 inches Jecths were 1,400 ana 700 
ft./secona rescsectively (axis horizontal) at 3 inches above the surface and-1,100 ana 500 ft,/ 
second respectively (axis horizontal) at 3 ft. 
Description of charses used. 
The charge used in each of the tests consisted of a oz, cylindrical oellet of C.., 
2 inches in diameter, and 12 incnes thick. 
Experimental procedure. 
The shock-wave velocity in air due tc the detonation of a submerged charge was measured 
using acetylene flames, a row of small acetylene jets burning vertically above the charge being 
extinguished by the oassaye of the snock wave. The time Interval between the extinction of 
Successive flames was recorded by a rotating orum camera, the slit of which was focussea on the 
burners. 
In the first series of experiments, the jets were soacea at 6 inches intervals, the 
lowest being 3 incnes above the water surface. with this arrangement 6 tests were carried out, 
3 with the axis of the chaaye vertical and its centre (a) 2 inches, (b) 4 inches and (c) 8 inches, 
below the surface and 3 witn the charge axis horizontal, ana the same 3 depths of Immersion. 
A further test was made with the charge axis vertical and aeoth of immersion 2 inches, 
but with the 8 jets used arranged at 1, 3, 5, 7, 9, 11, 24 and 36 inches respectively above the 
water surface, 
Serlous damage due to the disolacea water was sustained by the burmers and their 
Supoorting framework during each 2x2sriment. 
Records obtained. 
Two records, tyoical of those obtained, are shown in Figures 1 and 2, The time scale 
for each record was calculatea from the drum speed used, and the time interval between the 
extinction ws. 
