Dynamic characteristics of high-speed droplets impactingon solid surface

When aircraft passes through clouds or vehicles travel in rainy weather, droplets impact these transportation surfaces at high velocities, forming liquid films that impair driver visibility and threaten operational safety. However, existing studies have predominantly focused on low-speed droplet impact. To better understand the motion characteristics and influencing factors of droplets during high-speed impacts, this paper investigates the dynamic behavior of droplets impacting solid surfaces at high velocities. An innovative velocity generation device was developed by modifying a split Hopkinson pressure bar.

By integrating ultrasonic levitation technology with dual-view high-speed photography, the entire process from droplet impact to stabilization was dynamically captured. The study explores the influence of solid surface wettability on high-speed droplet impact. Experimental results reveal that during high-speed impact, the retraction rate of the droplet spreading factor is significantly lower than the spreading rate. The maximum spreading factor scales with the Weber number (We) according to We^0.23, which is consistent with the Clanet model, exhibiting an absolute relative error ≤10%. Furthermore, the number of fingers increases as a power-law function of the We, while the maximum finger length exhibits a nonlinear trend of initial increase followed by decrease. It was also found that solid surface wettability significantly affects droplet dynamic behavior and promotes finger branching. This research provides critical theoretical support and experimental evidence for optimizing inkjet printing resolution and designing anti-icing coatings.