Numerical analysis on dynamics and thermodynamics of a supercooled water droplet considering the dynamic contact angle

The dynamics and thermodynamics of a supercooled water droplet impacting on a horizontal cold surface are investigated numerically. A two-dimensional axisymmetric model that considers both the non-equilibrium solidification caused by the supercooling and the dynamic contact angle (DCA) caused by the hysteresis phenomenon is developed to simulate the impacting, spreading, retraction, and freezing processes by combining the coupled volume-of-fluid and level set air–liquid interface capturing method and the Enthalpy-Porosity phase transition method. The common Kistler DCA model is applied to iteratively calculate the real time contact angle of three-phase contact point using the contact line velocity. The DCA model makes the simulation results of the spreading factor more accurate compared with the experimental data than the static contact angle model does. The non-dimensional maximum spreading factors of the room temperature and supercooled water droplet are almost the same in the low Weber number region, but quite different in the high one. The stable spreading factor is independent of the Weber number but increases with the decrease in the contact angle and the increase in the supercooling degree. This study can deepen the understanding of the impacting-freezing mechanism of a supercooled water droplet.