Impact dynamics of a droplet on a heated surface

Abstract

The effect of impact velocity and substrate temperature on the impact dynamics of a water droplet on a non-heated and heated glass substrate is studied. A high-speed camera is utilized to record the time-varying droplet shapes during the impact. The initial spreading of the droplet is driven by large kinetic energy with large deformation of the free surface. The droplet recoils due to conversion of the surface energy to the kinetic energy and the internal flow reverses to radially inward. The liquid-gas surface oscillates along with the flow reversal from axially upward to axially downward, due to competition between the surface and kinetic energy. The amplitude of oscillation damps due to viscous dissipation and droplet assumes a spherical cap shape after it comes to rest. A lager impact velocity corresponds to higher kinetic energy and oscillations take longer time to dissipate. As the temperature of the substrate increases, the droplet spreads lesser due to larger resistance to the wetting at the contact line.