Numerical simulation analysis of symmetric impact of two droplets on a liquid film

Abstract

Analyzing the impact of a droplet on a liquid film is a typical free-surface problem. However, a few studies have investigated the impact of multiple droplets, and in most cases, the droplet impact direction is assumed to be vertically downward. The effect of the impact angle on the characteristic parameters of the spray remains unknown. In this study, the coupled level set and volume of fluid method is used to analyze the development of the gas–liquid interface when two droplets impact a liquid film, and the grid of the gas–liquid interface is refined using the grid adaptive refinement method. The accuracy of numerical simulation has also been verified. The numerical simulation results showed significant differences in the liquid splash morphology corresponding to the different impact modes. The inward impact of the two droplets promotes splashing, whereas the outward impact inhibits it. The liquid film thickness primarily affects the local splash morphology. The droplet spacing affects the spreading diameter and jet angle. The cylindrical jet formed by the symmetrical inward impact of the droplets is unstable, and the rupture mechanism of the cylindrical jet is elucidated for different impact modes. These results provide reference for the application of droplets impingement.