Title screen

Droplet collisions are common to many gas-liquid systems, based on spray flows injected into a gas-vapor environment. It is customary to distinguish between roles of precollision droplets (target and projectile) in such systems. As a rule, the target droplet has slower velocity than the projectile droplet or can even be stationary. Secondary atomization of droplets through their collisions with each other is a promising field of study. In particular, it is important to evaluate droplet effect roles on collision regime maps and characteristics of emerging child droplets (postcollision). This article presents experimental research on characteristics of binary collisions of water droplets that were obtained using high-speed recording. Ranges of droplet sizes, velocities, and impact angles are 0.11 mm, 0.1-5 m/s, and 0°-90°, respectively. We distinguish four interaction regimes of bounce, coalescence (CO), separation (SE), and disruption (DI). To determine child droplet characteristics, we address the DI regime in detail. The projectile droplet breaks up into many more postcollision droplets than the target droplet, with Weber (We) numbers ranging from 50 to 150. At We > 150, precollision droplet DI produces a similar number of secondary droplets. We plot separate regime maps of droplet collisions as a function of We for target and projectile droplets. Critical Weber numbers (Wecr) are determined, accounting for droplet roles. Greatest differences among Wecr are observed during transitions from CO to SE and SE to DI.