Impact of single and multiple drop array on a liquid film

The paper reports an experimental investigation of water drop array impact onto a thin liquid film. The dropswere of millimetric size and were impacting simultaneously on the liquid film. Different impact velocities(275<We<515) and film thickness were investigated. A high resolution CCD camera was used to visualize thephenomenon and image analysis techniques were then used to extract quantitative data from the images.Comparison with single drop impact, under the same experimental conditions, allowed to evidence the effect ofcrown-crown interaction of secondary atomisation and, generally, on the impact morphology. Liquid structuresare formed by the crown interaction and their subsequent break-up give rise to further secondary atomisation ifthe impact velocity is sufficiently high. The crown interaction can produce splashing also for impactingconditions under which single drop impact would not give rise to splash, thus lowering the splashing threshold..