Research on the characteristics of water droplets impacting moving superhydrophobic surfaces and its regulation

Icing poses significant hazards to aviation safety. Superhydrophobic surfaces have gained widespread attention for their capability to induce rebounding and detachment of impacting water droplets from surfaces, thereby achieving anti-icing. When icing occurs on equipment such as wind turbines and aircraft, the droplet diameter typically ranges from micrometers to tens of micrometers, and the surface is often in motion. However, experimental research on the characteristics of micrometer-scale water droplets impacting moving superhydrophobic surfaces remains vacant. Consequently, in this paper, we developed an experimental platform to investigate the impact of micron-sized water droplets on moving superhydrophobic surfaces. High-speed photography revealed that, contrary to observations with millimeter-scale droplets, the contact time of micrometer-scale water droplets impacting superhydrophobic surfaces increases significantly (by 78%) at high surface tangential velocities. Furthermore, numerical simulations were conducted to gain deeper insights into the impact process, particularly focusing on the influence of surface motion on the impact characteristics of water droplets. This influence mainly manifests in three aspects: it prolongs the centroid descent process, redirects water droplets from the expansion direction to the flow direction, and changes the expansion and retraction characteristics of water droplets. The extension of the contact time of micrometer-scale water droplets due to the high-speed motion of superhydrophobic surfaces is attributed to the intense stretching of the water droplets' front edge. Subsequently, by applying dual synthetic jets to water droplets, the tangential relative impact velocity between the droplets and the surface is decreased, resulting in a 28% reduction in the contact time.