Modeling of high-velocity impact ejecta by experiments with a water drop impacting on a water surface

We performed a series of experiments with water drops which impacted on the surface of a water pool with velocities up to 3.4 m/s and produced an ejecta cone. The use of a high-speed camera allowed us to clarify some features of the ejecta process that we observed in our previous high-velocity impact experiments with aluminum projectiles and targets (Shumikhin et al. in Int J Impact Eng 50:90–98, 2012). The experiments with water were motivated not only by the high cost of high-velocity impact experiments and the difficulty of registering in-situ in such experiments, but also by the similarity of the ejecta processes in water and aluminum. The modeling was based on the number of Weber (We) and Reynolds (Re). The critical number We for the splashing threshold means that there is a criterion for ejecta that connects the kinetic energy of the projectile with the fracture energy of the projectile and target. Experiments with water allowed us to describe the mechanism of decrease of the number of ejecta spikes and thus to explain the presence of V-shaped chains of small craters that we observed in the high-velocity impact experiments with aluminum projectiles and targets.