Simulation of the impact and icing processes of water droplets on spheres

The impact and icing phenomenon of water droplets is widespread in many fields and has a serious impact on production and life. On the basis of the Volume of Fluid method applied to capture the multiphase-interface flow, the dynamic contact angle model and the Solidification/Melting model are coupled to solve the droplet impact and icing characteristics on a curved surface with high precision. The effects of Weber number, contact angle, sphere-to-droplet curvature ratio, κ*, and supercooling degree on the impact and icing behaviors and the maximum spreading characteristics are systematically investigated. The results indicate that on the convex sphere, both the maximum spreading factor and arc angle rise with an increasing Weber number or a decreasing contact angle. The maximum spreading factor increases as κ* increases especially for κ*≳0.1 but remains almost unchanged for κ*≲0.1, while the maximum spreading arc angle keeps increasing. On the concave sphere, the maximum spreading factor increases slightly and then decreases with the increasing curvature ratio due to the combined effect of gravity and surface shape. When the droplet is supercooled and the spherical surface is cold, the supercooling degree slightly influences the spreading stage but has a substantial effect on the receding stage. The larger the Weber number and the curvature ratio, the more conspicuous the influence of the supercooling degree on the maximum spreading characteristics. This work may help us to deeply understand the mechanism and essence of the droplet impact and icing process on the spherical surface and benefit the design of the antiicing surface.