Multiple drops impact onto a liquid film: Direct numerical simulation and experimental validation

A simultaneous impact of three water drops (aligned with equidistant spacing) onto a solid wall covered by a thin liquid film is predicted by direct numerical simulation using the multiphase code Free Surface 3D (FS3D) which is based on the volume-of-fluid (VOF) method and uses the piecewise linear interface calculation (PLIC) method to reconstruct the interface. The numerically reproduced splashing morphology is qualitatively and quantitatively compared with available experimental data and theoretical models. The results show the reliability of the numerical tool (FS3D) to predict quantitatively the complex phenomena involved in detail, like the evolution of crown geometry and the liquid structures resulting from the interaction between the different crowns. The comparison evidenced also the most important critical aspects of the numerical simulation of such complex phenomena, not often reported or even considered in the available open literature (e.g. the early lamella rupture observed in the simulation, caused by a limited numerical resolution, antagonist to the inadequacy of related rupture models). This phenomenon is still a challenging research topic (from both the experimental and the numerical side) and its study is still a necessary step for gaining detailed knowledge for improving the stochastic simulations of multiple drops impact onto liquid films.