Curvature-dependent impact dynamics and freezing behavior of ellipsoidal droplets on supercooled spherical surfaces

• A systematic study on droplet impacting supercooled spherical surface is proposed. • Droplet aspect ratio and surface curvature jointly affect rebound/freezing outcomes. • Impact force peak pattern transitions at critical sphere-to-droplet diameter ratio. • Flat droplets exhibit higher initial heat transfer rate but lower amount over time. Ice accretion caused by supercooled droplet impact is a critical concern in aerospace, power, and wind energy systems, where curved surfaces frequently encounter complex icing conditions. This study numerically investigates the impact dynamics and freezing behavior of ellipsoidal droplets on convex superhydrophobic spherical surfaces using a coupled Volume of Fluid (VOF) and solidification model. Key parameters including aspect ratio (AR), dimensionless sphere-to-droplet diameter ratio ( D *), wall temperature ( T w ), and Weber number ( We ) are systematically varied to explore their influences on droplet morphology, spreading factor, impact force and thermal transport. The results reveal that flatter droplets exhibit stronger initial spreading and higher impact forces, while elongated droplets show delayed retraction and enhanced internal freezing. Lower D * values promote greater spreading and stronger retraction dynamics due to tangential gravitational components. The impact force evolves in two or three peak patterns depending on surface curvature, with D * < 4.7 favoring three-peak pattern. Additionally, surface curvature significantly modulates heat transfer, where higher D * surfaces lead to increased total heat transfer capacity and freezing extent. These findings provide new insights into the anti-icing design of curved surfaces commonly encountered in practical engineering environments.