3-D computational study of a single droplet impacting the random rough surface: Hydromechanical solidification

The spontaneous spreading of water droplets on a low-temperature solid surface is ubiquitous in nature and critical to numerous industrial applications, but its mechanism remains elusive. In this study, a three-dimensional (3-D) computational fluid dynamics (CFD) model, which intergrows a random rough surface, is proposed to investigate the effects of droplet impact dynamics on hydromechanical solidification. The 3-D CFD model reveals important physical details that cannot be captured easily by a 2-D axisymmetric model or by practical experiments. For instance, the established model provides a unique perspective on the complex hydromechanical solidification behaviours of a single falling droplet in terms of impact dynamic parameters and a solidified cloud map. In particular, the two-phase interfacial resistance derived from the liquid-to-solid transition is systematically discussed, demonstrating different wetting states for spreading droplets on a random rough surface. Moreover, the solidified cloud map suggests that surface wettability, substrate temperature, and droplet impact velocity have nonnegligible effects on phase transition solidification. This work may expand our understanding of droplet dynamic solidification on cold superhydrophobic surfaces and provide a great reference for related subsystems referring to anti-icing/frosting or self-cleaning technologies.