A 3D numerical model for computing simultaneous impact of multi-droplet on liquid film

Multiple droplets impinging on a thin liquid film simultaneously is numerically studied using a three-dimensional model with an implement of a random disturbance subjected to Gaussian distribution. This model is very effective to predict droplet splashing under relatively high impingement momentum, which is validated and has a good agreement with experimental observations and measurements. Results show that the simultaneous impingement of multiple droplets can lower the splashing threshold due to partial cracking of central liquid sheet under surface tension, and the induced vortexes in the gas phase also contribute to the entire cracking and splashing of the central sheet aside from the effects of instability. The height of the central sheet increases with increasing Weber number and/or film thickness, while increasing droplets horizontal interval results in a lower height due to weak interaction of fluids inside the film. Besides, a geometric model is built up to demarcate the impact region into semicircle regions and a series of rectangle regions during simultaneous impact, further to discuss the variations of area and residual film thickness in each region as well as the total area and average film thickness. This study provides the preliminary understandings of one important aspect of multiple droplets impact without consideration of solid-film heat transfer process.