Direct Self-Sustained Fragmentation Cascade of Reactive Droplets : Project Associate Professor Chihiro Inoue, Department of Aeronautics and Astronautics, and other researchers

A traditional hand-held firework generates light streaks similar to branched pine needles, with ever smaller ramifications. These streaks are the trajectories of incandescent reactive liquid droplets bursting from a melted powder. We have uncovered the detailed sequence of events, which involve a chemical reaction with the oxygen of air, thermal decomposition of metastable compounds in the melt, gas bubble nucleation and bursting, liquid ligaments and droplets formation, all this occurring in a sequential fashion. We have also evidenced a rare instance in nature of a spontaneous fragmentation process involving a direct cascade from big to smaller droplets. Here, the self-sustained direct cascade is shown to proceed over up to eight generations, with well defined time and lengthscales, thus answering a century old question, and enriching with a new example the phenomenology of comminution.

Physical Review Letters：https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.074502