Experimental investigation of the impact and freezing processes of supercooled water droplet on different cold curved surfaces

The impact of supercooled water droplets (SCWD) on aircraft cold surfaces constitutes a major cause of aircraft icing, posing a considerable threat to flight safety. Developing a safe, efficient, and energy-efficient anti-icing method necessitates an in-depth investigation of the icing mechanism of SCWD impacting cold curved surfaces. This study experimentally investigates the freezing behavior of SCWD on cold surfaces with diverse curvatures. The results show that the water droplet spreading factor (WDSF) significantly increases as surface curvature ranges from 0 to 125 while simultaneously decreasing the freezing time. Furthermore, the ice ring morphology from droplet freezing transitions from a raised crown shape to a concave cake shape at the center. Changing the impact position of droplet resulted in a marked increase in WDSF, a substantially reduced freezing time, and the emergence of strip icicles at the lower part. Additionally, this study examines the effects of Weber number (We = 459–650) and impact surface temperature (T_w = −30 °C–0 °C) on the impact freezing process. An increase in We leads to a higher WDSF and reduced freezing times, while lower surface temperatures decelerate droplet retraction, thereby shortening freezing time. At surface temperatures below −25 °C, T_w results in droplets splashing upon impact and rapidly freezing during the spreading stage. The findings of this research provide experimental insights crucial for developing aircraft anti-icing technology.