Fate of secondary droplets produced by high-speed raindrops interacting with a liquid pool

Secondary droplets produced by interactions between falling fluid drops and a liquid pool play a significant role in engineering applications and geophysical processes in nature. This study uses direct numerical simulations to investigate the dynamics of secondary droplets generated by raindrop–liquid pool interactions. The raindrop parameters feature realistic speed tilde 7 normal m normal s Superscript negative 1 ∼ 7 m s − 1 ${\\sim} 7\\ \\mathrm{m \\ s}^{-1}$ , effective diameters tilde 1 ∼ 1 ${\\sim} 1$ – 4 normal m normal m 4 m m $4\\ \\mathrm{mm}$ , and surface tension values ranging from 25 percent sign 25 % $25\\,\\%$ to twice the typical air–water interface value. The numerical configurations include both a single raindrop and two raindrops separated by distances between two and four times the raindrop diameter. The secondary droplet size distribution upper N Subscript d N d $N_d$ is found to scale with the droplet radius r Subscript s r s $r_s$ as upper N Subscript d Baseline left parenthesis r Subscript s Baseline right parenthesis proportional to r Subscript s Superscript negative 5 divided by 2 N d ( r s ) ∝ r s − 5