Observing the impact force and low-speed droplet behavior of wet surfaces with very-thin liquid films

The impact of a low-speed droplet on a very-thin liquid film on a solid surface was analyzed experimentally by observing the impact force and droplet behavior. A high impact force and delayed peak impact time were observed with very-thin liquid films (with h/d < 0.05; his the liquid-film thickness and d is the droplet diameter). On increasing the film thickness, the impact force gradually increased. The increased impact force could be attributed to splash formation on the wet surface arising from lateral-jet formation at the instant of droplet impact, and interactions with the liquid film. Furthermore, this result was in agreement with numerical simu-lation results of the surface impact-pressure variation which indicated impact-pressure damping immediately after droplet impact, with a subsequent spread of the wet-surface impact-pressure area, thereby causing an in-crease in the impact force at a later stage. Thus, impact-pressure damping and force increments occurred at different time ranges after droplet impact.

Automated summary

The impact of a low-speed droplet on a very-thin liquid film on a solid surface was experimentally analyzed to understand its behavior and impact force. It was found that very-thin liquid films have high impact forces and delayed peak impact times. Increasing the film thickness resulted in gradually increasing impact forces, which can be explained by splash formation and interactions with the liquid film. The simulation results of surface impact-pressure variation were in agreement with the experimental observations, showing a damping of impact pressure immediately after droplet impact, followed by an increase in impact force at a later stage.