Onset and evolution of counter-rotating baroclinic vortex pair in shock induced aerobreakup of droplets

摘要

The interactions between shock and a droplet result in counter-rotating baroclinic vortex pairs. In this work, to better understand the initiation of the stripping droplet breakup regime, the onset and evolution of the counter-rotating baroclinic vortex pair produced via the interaction between a shock wave and a spherical water droplet was numerically studied. The water droplet and surrounding air were simulated using a shock- and interface-capturing scheme for compressible multi-component Euler equations. The sequence of the droplet interaction events and the evolution of the counter-rotating baroclinic vortex pair were analyzed. The time variation of circulation was computed as a function of the shock Mach number; it was decomposed into positive and negative components. Moreover, the circulation of the counter-rotating baroclinic vortex pair was extracted using spatial filtering. The counter-rotating baroclinic vortex pair was initiated as a result of the baroclinic effect caused by two different shock-droplet interactions: the interaction between the incident shock and the droplet and the interaction between the droplet and the diffracted shock moving radially outward. Lastly, circulations of the counter-rotating baroclinic vortex pair were computed for various shock Mach numbers. These results provide a better understanding of the stripping droplet breakup regime in the interactions between shock and a droplet.