Numerical investigation of droplet impact on a solid superhydrophobic surface

Abstract

The impact of microscale water droplets onto a solid superhydrophobic surface is numerically investigated. The multiphase problems are modeled by the three-dimensional incompressible Navier-Stokes equations and the liquid-gas interface is captured by the level set method. The numerical model is verified with our experimental impact results via the comparison of spreading factor ζ, which is defined as the ratio of the wetted surface area to droplet initial diameter. The simulation results suggest that when the droplet impacts with constant impact velocity and diameter, the maximum spreading parameter increases with the ambient temperature. As Weber and Reynolds numbers increase, the impact turns into doughnut-breakup regime; the droplet breaks up into a toroidal shape and a cavity is formed at the center. The results indicate that the diameter of the central cavity grows linearly related to the non-dimensional time. Finally, a new droplet impact spread/splash model that is governed by Weber and Reynolds numbers is proposed for superhydrophobic surface based on our numerical and experimental results.