Recent Development on the Study of Supercooled Large Droplets: Impacting, Splashing, Surface Water Dynamics, and Ice Accretion

Supercooled large droplets (SLDs), typically defined by diameters exceeding 100 µm, represent a significant meteorological hazard to aviation safety. Unlike conventional cloud-sized droplets, SLDs exhibit higher inertia, causing them to follow ballistic trajectories that result in impingement well aft of standard leading-edge ice protection systems. Furthermore, SLDs are characterized by complex microphysics, including high-speed splashing into secondary droplets and a distinct thermodynamic response where immediate solidification is inhibited, leading to hazardous surface water runback. This paper provides a comprehensive review of recent progress in understanding SLD phenomena. We examine the fundamental mechanisms of droplet impact on dry and wet surfaces, the effects of oblique impingement and ambient air conditions, and the evolution of surface water dynamics. Additionally, the review evaluates the efficacy of emerging ice protection technologies, such as superhydrophobic and liquid-infused surfaces, in mitigating SLD-induced ice accretion. By synthesizing these recent developments, this review aims to bridge the gap between fundamental droplet physics and practical aviation safety strategies.