COLLISION MORPHOLOGIES SUPERCOOLED WATER DROPLETS ON SMALL LOW-TEMPERATURE SUPERHYDROPHOBIC SPHERICAL TARGETS

Abstract

The collision and freezing of supercooled water droplets exist in many fields and are usually uncon-ducive. The superhydrophobic surfaces used for anti-icing generally have microstructures or local protrusions which could be simplified as small spherical targets comparable to the droplet in size. The supercooled water droplets' collision and freezing on small low-temperature superhydrophobic spherical targets with the sphere-to-droplet diameter ratio D* ≤ 1 are studied numerically in this work. Coupling the solidification-melting model, the Volume of Fluid (VOF) method is used to implement numerical simulations. The supercooling degree, Weber number, and sphere-to-droplet diameter ratio effects on the collision and freezing behaviors and the area coverage ratio of the droplet on the low-temperature small sphere are investigated. Six typical morphologies are identified: full dripping, partial dripping, lower adhesion, wrapping adhesion, upper adhesion, and rebound. The water droplet is found to be more likely to drip down with the increasing Weber number, and the decreasing supercooling degree and the decreasing diameter ratio. A comprehensive morphology map is eventually established to illustrate the combined influence of the Weber number and diameter ratio on the occurrences of the rebound, adhesion, and dripping for different supercooling degrees. This work provides theoretical guidance for the engineering design and structural optimization of anti-icing surfaces.