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 (<i>Oh</i>), surface temperature (<i>T</i>), and Weber number (<i>We</i>) 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 <i>Oh-T-We</i> 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 ≤ <i>Oh</i> ≤ 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.