Droplet splashing on moving and inclined surfaces

Droplet splashing on moving and inclined surfaces at atmospheric and reduced pressures was investigated using high-speed photography. It was found that the splashing morphology on a moving surface was very similar to that on an inclined surface regardless of the ambient pressure as long as the equivalent inclination angle, defined as the angle between the surface velocity and the resultant velocity of the impacting droplet, was the same as the surface inclination angle. The abnormal splashing known to occur on inclined surfaces at reduced pressure, both wing splashing and upward-only splashing, was also observed on moving surfaces. The variations of splash angle, marking the transition between the splashing and non-splashing zones of the lamella, were determined as a function of the Weber number, the equivalent inclination angle, and the ambient pressure. The measured splash angles were similar for impacts on moving and inclined surfaces, indicating a similarity between splashing on both types of surfaces. Two theoretical models of inclined impact were extended to include surface movement and were validated through comparison with the experiments.