Shock-induced aerobreakup of parallel-arranged droplets

The aerobreakup dynamics of parallel droplets subjected to shock-induced airflow is investigated through experiments, in which the parallel-arranged droplets with controllable size and spacing are generated through forced breakup of a free liquid jet. Utilizing high-speed photography, the breakup process of parallel droplets over wide ranges of spacing ratio and Weber number can be captured. At low Weber numbers, the droplet fragmentation mode shifts gradually from the traditional bag breakup to the trailing and shuttlecock modes as the spacing ratio decreases. At relatively high Weber numbers, the breakup mode changes from an open to a closed configuration, depending on whether the channel between adjacent droplets closes during the deformation process. A phase diagram of droplet fragmentation modes is constructed in the parametric region of Weber number versus spacing ratio, with the boundaries between different modes clarified theoretically. Quantitative analyses on droplet deformation further demonstrate that reducing the spacing ratio could accelerate filament formation and facilitate channel closure. Overall, this work offers insights into the interaction dynamics of droplet clusters, thereby providing useful guidance for applications such as fuel atomization.