Promoting rebound from droplet impact on a spherical particle: Experimental and numerical study

In this study, we experimentally and numerically investigate the activity of a rebounding droplet on a spherical particle and the effects of surface curvature on its rebounding behavior. We report that the rebound of the droplet can be promoted in smaller particles. As the droplet-to-particle size ratio increases, the critical Weber number is significantly reduced, and the restitution coefficient is much increased. The underlying physical mechanism for the promotion of the rebound is the reduced energy dissipation on the smaller particles in the very early stages of the collision, and this reduction mainly occurs as the liquid is being squeezed. This reduced energy loss allows larger liquid-gas interfacial deformation at the maximum spreading state and also allows more drastic retractions during the recoiling stage, which eventually leads to the promotion of the rebound.