The interaction between droplets and the vortex ring after a shock wave

To elucidate the characteristics of droplet breakup induced by a shock wave and vortex ring behind the shock, experiments were conducted with water and various glycerol mixtures under different shock Mach numbers. High-speed visualization system, pressure testing system, and laser particle analyzer were applied to record the interaction process between droplets and a vortex ring after a shock wave. The results show that two stages of interaction are identified, including droplet-shock wave interaction and droplet-vortex ring interaction. Small clusters of droplets separated from the mother droplet will exhibit "white dot" and "swing arms" structures when subjected to vortical flow. At high shock Mach numbers, which generate strong circulation, the centrifugal force from rotation will cause droplet deformation and fragmentation. However, droplets with higher viscosity impede the stretching effect of the vortical flow, resulting in less deformation and fragmentation. Our data could provide valuable insights into droplet breakup in internal combustion engines and other industrial operations.