An Experimental Study on Transient Wind-Driven Water Droplet Runback and Dynamic Ice Accretion Process Over a Frozen Cold Surface

The runback and freezing behavior of water droplets on aircraft surfaces critically impact ice accretion and aerodynamic performance during flight in cold environments. This study experimentally investigates the dynamic freezing process of runback water droplets on a cold flat plate under controlled ambient temperatures of −5 °C, −10 °C, and −15 °C. Using synchronized Digital Image Projection (DIP), Particle Image Velocimetry (PIV), and infrared (IR) thermography, the coupled fluid-thermal interactions governing droplet deformation, transport, and phase change were quantitatively characterized. Results show that freezing onset time decreases markedly with lower ambient temperatures, significantly reducing runback distance. The flow field around the droplet exhibits complex structures that evolve with droplet deformation and ice formation. Thermal imaging reveals localized ice nucleation sites and radial propagation of freezing accompanied by latent heat release. These insights enhance understanding of microscale icing phenomena and inform more accurate predictive models for aircraft ice accretion mitigation