Supercooled water droplet impacting-freezing behaviors on cold superhydrophobic spheres

Abstract The impacting-freezing behaviors of supercooled water droplets on superhydrophobic spheres are investigated. A numerical model using the VOF (Volume of Fluid) method and enthalpy–porosity technology is established and validated by comparing the droplet profiles and spreading area factors by simulations and experiments. The effects of Weber number, supercooling degree and sphere-to-droplet diameter ratio (D*) on the impacting-freezing dynamics, including the droplet profile, spreading area factor and final rebound/adhesion, are studied. The results indicate that the supercooling rarely influences the spreading stage but significantly affects the receding stage with a larger stable spreading area factor obtained at a greater supercooling degree. With the decreasing of diameter ratio, the droplet generates a larger maximum spreading arc angle, a higher receding speed and thus a shorter contact time. The maximum spreading area factor greatly increases with reducing diameter ratio for D*