Similarity between the primary and secondary air-assisted liquid jet breakup mechanisms

We report an ultrafast synchrotron x-ray phase-contrast imaging study of the primary breakup mechanism of a coaxial air-assisted water jet. There exist great similarities between the primary (jet) and the secondary (drop) breakup, and in the primary breakup on different length scales. A transition from a ligament- to a membrane-mediated breakup is identified around an effective Weber number We'similar to 13. This observation reveals the critical role an effective Weber number plays in determining the atomization process and strongly supports the cascade breakup model.