Experiment study of droplet impacting on wetted surface

A high-speed camera was used to observe the process of three different sizes of droplet impact at different speeds on the wetted surface (horizontal and different tilt angles) at 11000 frames per second. Three experimental phenomena, including spreading, crown without splashing and splashing, were studied. The effects of initial droplet diameter, droplet impact velocity and inclination angle of the surface on splashing phenomenon were qualitatively analyzed. The critical parameters of splashing phenomenon resulted by droplet impacting on wetted surface were counted quantitatively, and the empirical relation of the splashing criterion was given whose error analysis was also made. The results show that with the increase of the impact velocity of droplets, after impacting on the wetted surface, the phenomena of spreading, formation of liquid crown without splashing and splashing with secondary droplet generated occur in sequence. The increase of the droplet diameter and the decrease of the surface inclination angle both promote the emergence of splashing. By fitting the experimental data, the relationship between the dimensionless parameter K, which is used to determine whether the splashing occurs after the droplet impacting on the wetted surface, and the dimensionless liquid film thickness H^* is acquired: K = 3210-122284.48 H^* + 2.23426 × 10⁶ H^*2 (0.008 56 < H^* < 0.03318). (authors)