Vaporization of a liquid drop suddenly exposed to a high-speed airstream

Many studies of fragmentation of liquid drops at supersonic Mach numbers report the appearance of large amounts of mist. Photographs from other studies, which do not mention mist at all, strongly suggest that copious amounts of mist are formed at the earliest stages of fragmentation. In this paper, we present arguments and calculations which indicate that this mist is formed from condensed vapour arising from the flash vaporization of the hot and low-pressure liquid on the leeside of the drop. Low leeside pressures are produced by the rarefaction of the gas, the acceleration of the drop, and the high tensions generated by rapid stretching of the stripped liquid. The droplet temperature may rise because of heat transfer from the hot gas to thin drop filaments, and by viscous heating due to rapid deformation.