437 



THE RATE OF RISE OF LARGE VOLUMES OF GAS IN WATER 



H. N. V. Temperley and LI. G. Chambers 



January 1945 



Summary , 



The work described By Taylor and Davies (i) is extended to volumes of gas of the order of 

 gallons. The necessary large volumes of gas were obtained Dy overturning a bucket under water and 

 By i ounce charges of burning cordite. The resulting bubbles were photographed in the glass-fronted 

 tanks of the M.A.E. Establishment at Glen Fruin. The relation u = ^/ /ga between velocity and 

 radius, found experimentally and theoretically by Taylor and Oavies, was confirmed for bubbles with 

 cap radii of up to 15 cm,, and it was concluded that such bubbles are near the limit of stability. 



The work appears to be in general agreement with existing knowledge of the behaviour of the 

 gaseous products from very deep explosions. it is concluded that the bubbles from such explosions 

 break up Into comparatively small fragments, once the oscillation has ceased. 



An attempt is made to improve the theoretical solution of the hydro-dynamic equations found 

 by Taylor and Davies, but it appears that the convergence of the method Is rather slow. 



Introduction . 



The work described in this report was carried out in continuation of that by Taylor and 

 Davies (l). The largest volume of gas used by them was of the order of 100 cc, and it was desired 

 to extend the work to much larger volumes of gas to gain a more complete idea of what happens in the 

 final stages of an underwater explosion. Thus, the volume of gaseous products released from one gram 

 of Amatol (neglecting water) is given by Taylor and Oavies as 650 cc. Thus *e conclude that an 

 ounce of explosive will liberate roughly four gallons of gaseous products at atmospheric pressure. 

 In order t» deduce .'.hat happens during the final stages of an underwater exolosion, we wish to know 

 whether such large volumes of gas can exist as coherent bubbles, or, If not, what is the volume of the 

 largest bubble that can exist and rise through the water without breaking up. 



Methods of carrying out the Trial . 



The relative fragility of the glass windows in the Glen Fruin tanks precluded the use of any 

 form of high explosives and therefore two alternative methods were employed. 



(a) The method described by Taylor and Davies (l) was tried on a larger scale. A bucket 

 (capacity Ji gallons) was lowered upside down to the bottom of the tank, a sinker being 

 attached to the handle. A sirall out-of-balarice weight {« lbs.) was attached to the end 

 of a short lever pivoted at the bottom of the bucket. while the bucket was being lowered 

 this lever was supported by a string, and the bucket remained inverted with the air trapped 

 underneath It. When the string was released the lever fell to a horizontal position and 

 the out-of-ba.^.nce weight tipped the bucket upwards 'emptying out" the air. 



(b) i ounce Burning cordite charges were ignited electrically by means of a "puffer-. Twp 

 types of container were used, a "pill-box" type of bakelite container which broke easily 

 when the charge was fired, and a stout brass cartridge-case the only exit from which was 

 a hole of i" diameter. 



The 



