Experimental Investigation on Water–Glycerol Droplets with Varying Viscosities Impacting a Supercooled Superhydrophobic Surface

Droplet rebounding from superhydrophobic surfaces represents a promising approach in anti-icing applications. The liquid viscosity and surface supercooling significantly influence the rebounding behavior. This study investigates the impact of a water–glycerol droplet with varying viscosities on a cold superhydrophobic surface through experimental methods. The effects of the Ohnesorge number (Oh), surface temperature (T), and Weber number (We) on the rebound dynamics are elucidated. For low-viscosity droplets, both spreading and receding times remain relatively constant; however, for high-viscosity droplets, the receding time increases with viscosity. Surface temperature has no significant effect on spreading time, but strongly influences receding time at low temperatures. Based on energy analysis, an Oh–T–We phase diagram is established, delineating three regions: full rebound, partial rebound, and full adhesion. Additionally, a theoretical model for the contact time of viscous droplets impacting cold superhydrophobic surfaces is extended to cover a broader viscosity range (0.0021 ≤ Oh ≤ 0.0051). This work pioneers the study of contact time for viscous droplets on cold superhydrophobic surfaces, providing a quantitative method for calculating contact time in anti-icing applications.