Photographic Investigation of the Projection of Droplets by Bubbles Bursting at a Water Surface

Abstract

Bubbles of air reaching the air-water interface burst and eject liquid droplets into the air to heights large compared to their diameter. Photographic evidence is introduced to prove the existence of a jet of liquid which upon breaking up produces these droplets. The jet is shown to be produced by the collapse of the bubble cavity. The droplets are found to be of the order of one tenth of the bubble size, for the range investigated (0.2 to 1.8 mm diameter), each bubble producing about 5 droplets. The droplet-producing mechanism is essentially the same for fresh and sea water or sea water with oleic acid surface film. The time required for the bubble to burst and the jet formation to take place is found to be proportional to the bubble size. The sea water droplets produced by this mechanism leave, upon evaporation of the water, salt nuclei having the size range observed by WOODCOCK (1952). It is suggested that such bursting of bubbles plays an important role in the natural production of air-borne sea-salt nuclei at the sea surface.