Dynamics of a water droplet on a hydrophobic inclined surface: Influence of droplet size and surface inclination angle on droplet rolling

An understanding of the dynamic motion of a water droplet is critical to reduce the effort required to remove dust particles from such surfaces. In line with self-cleaning applications, the wobbling and geometric variations of a rolling droplet were experimentally assessed for various droplet sizes. Furthermore, the internal fluidity of a rolling droplet was numerically predicted. The findings revealed that the rotational Bond number influenced the droplet wobbling due to adhesion force variations during rolling. Small-sized droplets, which were comparable to the capillary length, resulted in higher rotational speeds than those of larger-sized droplets. The ability to alter the rolling characteristics of droplets on inclined hydrophobic surfaces could address the limitations of self-cleaning surfaces and has implications for efficiency enhancements in solar energy devices.