Drop deformation and breakup due to shock wave and steady disturbances

Abstract

An experimental study of drop deformation properties induced by both shock wave and steady disturbances is described. Three test facilities were used, as follows: a shock tube facility for measurements of effects of shock wave disturbances on drops in gases, a 10 m high drop tube facility for measurements of effects of steady disturbances on drops in gases and a 1 m high drop tube facility for measurements of effects of steady disturbances on drops in liquids. Various dispersed and continuous phase gases and liquids were considered to provide dispersed/continuous phase density ratios of 1.15–12,000, Ohnesorge numbers of 0.0006–600, Weber numbers of 0.004–700 and Reynolds numbers of 0.03–16,000. At low Ohnesorge numbers (<0.1) for all types of disturbances, significant drop deformation (5%) began at Weber numbers of roughly unity, with the deformation regime ending due to the onset of breakup at Weber numbers of 10–20. These transitions were relatively unaffected by the Ohnesorge number for steady disturbances, however, increasing Ohnesorge numbers caused progressive increases of the Weber number range for both deformation and breakup regimes for shock wave disturbances—an effect that could be explained using phenomenological theory. Another transition, between dome- and bowl-shaped drops (related to the transition between bag and shear breakup), was correlated mainly in terms of Weber and Reynolds numbers for present conditions. Drop deformation for steady disturbances was relatively independent of dispersed/continuous phase density ratios but generally was smaller than for shock wave disturbances at comparable conditions due to the absence of overshoot from inertial effects. In contrast, drop drag coefficients, normalized by the drag coefficient of a solid sphere at the same Reynolds number, were correlated quite well by the degree of deformation alone.