Hybrid Experimental–Numerical Investigation of Droplet Impact Dynamics on Heated Spherical Surfaces

Droplet impact and spreading on spherical surfaces, often accompanied by heat transfer, are crucial in both industrial and natural settings. This study investigates droplet impact dynamics on a heated spherical surface under gravity at low Weber numbers. A new experimental setup was developed to capture the droplet spreading process, which was combined with a volume-of-fluid-based direct numerical simulation incorporating multiphase heat transfer. This hybrid experimental–numerical approach validated the simulation accuracy and enabled a quantitative analysis of key parameters—including spherical surface temperature, diameter ratio, and Weber number—on droplet spreading behavior. Parametric analyses reveal that an increase in spherical surface temperature slightly enhances the maximum spread coefficient. The maximum spread coefficient grows significantly with the Weber number but remains largely unaffected by the particle-to-droplet size ratio. Furthermore, the total heat flux strongly correlates with the droplet spreading area, reaching a peak at the maximum spread length.