Numerical study of the effect of surface wettability on droplet impact on a spherical surface

The phenomena of droplet impact are wildly found in nature and industrial field, surface wettability plays a significant part on the dynamic characteristics of the droplets after impacting. In this paper, effect of surface wettability on the dynamic characteristics of droplet after impacting spherical surfaces is explored, through two-dimensional numerical simulation with Coupled Level-Set and Volume-of-Fluid (CLSVOF) method. The degree of surface wettability is represented by the contact angle (CA). It is found that when the impact velocity is a constant, with the increase of the contact angle, the liquid film is more prone to break up and rebound after impacting a spherical surface. The maximum spreading factor and time needed to reach the maximum spreading factor both decrease with the increase of the contact angle. The Rebound height and rebound time increase with the increase of the contact angle. In a word, the increase of the contact angle hinders droplet spread, but promotes droplet break-up and rebound, someway. When the contact angle is a constant, with the impact velocity increasing, the maximum spreading factor increases while the time needed to reach the maximum spreading factor decreases. It is also found that when the contact angle is a constant, the time needed to reach the maximum spreading factor increases with the curvature ratio, ε. When the contact angle is between 30 and 150°, the maximum spreading factor increases with curvature ratio, while when the contact angle ranges from 0 to 30°, the maximum spreading factor decreases with the increase of the curvature ratio.