Study on the behavior of liquid films with different viscosities after impact by single droplet

Research on single drop impact, especially in the past two decades, has been motivated by a need for better predictive capability in many industries. The objective of this work is to clarify the single droplet impingement behavior onto a liquid film with different physical properties. Fluorescent agent is added to the liquid film, and the experimental method of Laser induced fluorescence(LIF) is used to distinguish the liquid film from the incident liquid droplet. Within the experimental ranges tested, the liquid film can be divided into five types after the droplet impacts, and the instability mechanism responsible for the crown and splash formation was analyzed. New results on crownsplash thresholds are obtained on the basis of the Weber number of incident droplet (We) and the Ohnesorge number of the liquid film (Oh*). Moreover, this article also explores the maximum height of the liquid film crown after the impact of the droplet and the crown diameter at the corresponding moment. They were analyzed by combining We with Oh*, and experimental results allow to propose empirical correlations which can be used for prediction of crown parameters.