Oblique impact of two successive droplets on a flat surface

Using the lattice Boltzmann method, a numerical study was conducted to investigate the oblique impact of two successive droplets on a flat surface. The focus was placed on the effects of surface inclination, lateral/longitudinal offset, the impact dynamics of the two droplets and the subsequent dynamics of the combined droplet. The evolution of the topology, contact lines and spread factor of the two droplets under various conditions was compared and analyzed. It was found that, compared to single droplet impact, the impact of successive droplets shows quite different dynamics due to the involved coalescence process. The surface inclination causes asymmetric spreading of the droplets. The increase in surface inclination leads to faster downward spreading and reduced lateral spreading. The non-zero offset between the two droplets further enhances this asymmetry. Furthermore, the intermixing between the two droplets during the oblique impact was also examined. It was observed that the surface inclination changes the mass distribution of the combined droplet.