Investigation of break-up, splash, and fingerlike instabilities for a large water slug impact

The fluid physics of splashing, spreading, and dispersion of a large-scale water droplet is investigated both experimentally and with model simulation. Several new phenomena of the droplet impact beyond conventional Rayleigh-Taylor instability theory are reported. First, our experimental data show that the number of fingers or instabilities along the spreading rim cannot be predicted by Allen's (1975) Rayleigh-Taylor equation. Second, we report that the surrounding medium (air) along with impact angle and droplet shape upon impact affect ejection velocity and splashing. Finally, the fundamental instability of the finger formation along the spreading rim may be due to interactions initiated by the compressed and displaced air, rather than the spreading of the liquid decelerating through the air. Several important correlations between the droplet impact velocities, the amount of spray ejected, the spray ejection speed, and the number of fingers or instabilities are presented.