Dynamics of falling droplets impact on a liquid film: Hybrid lattice Boltzmann simulation

The dynamics of falling droplets impact on a liquid film is numerically studied in this work. One or two two-dimensional droplets are initially placed above a liquid film and fall freely under gravity. To conduct numerical simulations, a hybrid method is adopted, in which the flow field is solved by using the lattice Boltzmann method and the interface is captured by solving the Cahn-Hilliard equation directly. At a fixed value of the thickness of liquid film (h*) and the mean distance between the droplet and the liquid film (H*), the effects of density ratio of droplet to ambient fluid (p*), Bond number (Bo, ratio of gravity to surface tension of droplet) and droplet arrangement on the dynamic behaviors of droplet impact are systematically investigated. In the falling process, dependent to the density ratio, both the elongation and compression of droplet can be observed. After the droplet impact, the occurrence of splash is determined by the Bond number. On the other hand, in the case of two falling droplets impact, a strong center-jet or a deer-horn-like crown structure is produced for the side-by-side or tandem arrangement. (C) 2015 Elsevier B.V. All rights reserved.