Impact dynamics of self-rotating droplets on superhydrophobic surfaces

Droplet impact on superhydrophobic surfaces has attracted significant attention due to its relevance to a wide range of engineering applications, such as anti-icing, self-cleaning and hydroelectric generation. In practice, droplets rarely fall vertically without initial motion. Aerodynamic and external disturbances often impart rotation, which significantly influences their impact dynamics. However, the impact dynamics of droplets with initial angular velocity on superhydrophobic surfaces remain poorly understood. Here, we investigate the dynamics of self-rotating droplets impacting superhydrophobic surfaces through numerical simulations, covering a broad range of droplet initial angular velocities from 0 to 700 rad/s. We find that increasing the droplet initial angular velocity leads to stronger centrifugal forces and higher rotational kinetic energy, which affects the balance between inertial and capillary forces, thereby enhancing droplet spreading and significantly reducing the contact time. Further, we systematically analyze how angular velocity influences both spreading and retraction stages, revealing critical mechanisms governing droplet behavior under rotational conditions. Based on these mechanisms, scaling laws are derived to accurately predict the maximum spreading coefficient and the contact time, demonstrating excellent agreement with the simulation results. These findings enhance the understanding of self-rotating droplet dynamics on superhydrophobic surfaces and provide guidance for related practical applications.