Drop Impact on Supercooled Surfaces

Frost formation and accretion present major economic and performance challenges for several industries, including aerospace, power transmission, and building environmental control. In the recent years, due to significant progress in nanoengineering and chemical functionalization, much attention has been given to the rational development of anti-icing surfaces via reduction of ice adhesion and delayed frost formation. Yet, comprehensive understanding of the impact and freezing dynamics of ambient-temperature water droplets on highly-supercooled (>100K) surfaces is limited. Here, we experimentally study ambient (≈ 22°C) water droplet impact on supercooled nanoengineered metallic surfaces (°C) having a range of wettabilities (). To characterize the freezing processes, we measure the dependence of freezing time and contact area of water droplets during impact. By varying the incoming droplet Bond number (0.5 < Bo < 5), Weber number (10 < We < 1000) and Ohnesorge number (0.001 < Oh < 0.01), we establish the underlying physics, characterized by the delicate interplay of not only liquid inertia, viscosity, surface tension, and gravitational body forces, but also on the substrate wettability and temperature, on freezing dynamics.