Investigation of effects of receding contact angle and energy conversion on numerical prediction of receding of the droplet impact onto hydrophilic and superhydrophilic surfaces

The aims of this paper is to investigate the influential factors on numerical prediction of the receding of a droplet impact onto the hydrophilic and superhydrophilic surfaces. In order to accomplish this target, the hydrophilic and superhydrophilic copper surfaces are fabricated and the droplet impacts onto the fabricated surfaces are recorded by the experimental observation system. Using the volume-of-fluid(VOF) method with the smooth function, the impacts of the droplet onto the hydrophilic and superhydrophilic surface are predicted. Associated with the experimental data and the numerical results, from two aspects of the dynamic contact angle and energy conversion among the kinetic energy, static pressure, surface energy and viscous dissipation, the characteristics of the receding of the impacting droplet are summarized. It is found that the numerical extra viscous dissipation induced by the parasitic currents have an obvious influence on the height of the apex of the receding droplet for the three dimensional computational domain, and the receding dynamic contact angle play an important role on the moving direction of the triple-phase contact line in the receding. Finally, considering both the space dimensional and dynamic contact angle effects, the 2d axisymmetric computational domains and proper dynamic contact angles are used to present the local energy distributions of the droplet impact on hydrophilic and superhydrophilic surfaces, and the mechanism of the energy conversion inside the droplet is discussed.