From spreading to splashing Droplet interactions with complex surfaces

Although droplet impact is the scourge of Dutch commuters, it is a fascinating phenomenon from a scientific point of view. Understanding droplet impact on a surface could have a myriad of interesting practical applications such as rain drops impacting on porous stone, spray cooling of hot surfaces, crop spraying, ink-jet printing, forensic research and more. In this thesis, we investigate the interactions between a droplet and (complex) surfaces, where the outcome of a droplet impact is dependent on a wide array of fluid and surface parameters. At low impact velocities, we investigated the influence of the surface wettability and entrapped air layer on droplet spreading. At high impact velocities, we investigated droplet splashing and how the fluid and surface properties influence the critical velocity at which smaller, secondary droplet split off from the main droplet during impact. Finally, we also discuss the liquid imbibition into cylindrical and square capillaries, where we investigate how the liquid imbibition inside the corners of the square capillary (corner flow) affects the liquid imbibition inside more complex capillaries geometries, and where the influence of surfactants on capillary rise is investigated as well.