Spreading and breakup dynamics of successive droplets impacting a curved surface

Abstract

The dynamics of droplet impact on curved solid surfaces is a phenomenon of considerable importance in fields such as agriculture, manufacturing, and environmental science, yet it is poorly understood. This study provides a numerical investigation into the complex behavior of successive droplets impacting a curved surface, examining key parameters such as contact time, coalescence time, pinch-off time, and breakup morphology. Key findings reveal that the inertia of the droplets influences the contact, coalescence, and pinch-off times, with higher values leading to shorter interaction durations. Additionally, droplet behavior changes with varying surface curvature and contact angles, including modifications in droplet spreading and breakup phenomenon. The critical value of the radius of curvature of the substrate for the transition to peripheral breakup regimes is found to vary non-monotonically with the contact angle. Furthermore, the size ratio between the leading and trailing droplets plays a significant role in influencing the pinch-off time and morphology of the droplet. Specifically, we have obtained a range of β_max (the ratio of the maximum spreading diameter to the initial droplet diameter), which varies from 1.375 to 3.113, depending on the droplet inertia, surface curvature, substrate contact angle, and size ratio of the droplet. These results deepen our understanding of droplet interactions on curved surfaces, not only contributing to advancing theoretical models but also offering practical applications in diverse areas, including pesticide spraying, fuel injection, and medical droplet administration. By addressing the gap in understanding successive droplet impacts on curved geometries, this work paves the way for further exploration and optimization of droplet-based technologies.