Oblique drop impact on thin film: Splashing dynamics at moderate impingement angles

Abstract

The oblique drop impact on the thin film is numerically investigated in this paper with special attention paid to its splashing dynamics at moderate impingement angles (45° ≤ α ≤ 75°). A three-dimensional multiphase lattice Boltzmann flux solver associated with the diffuse interface method is adopted after being validated against reference data. Efforts are made to recover the complex flow features in the oblique drop impact on the thin film at various impingement angles, film thicknesses (δ), Ohnesorge numbers (Oh), and Weber numbers (We). We found that the later stage of radial propagation of the jet base and the free rim is dominated by inertia and can be well correlated with dimensionless time τ through the square-root law. The elevation of the free rim exhibits a linear relationship with time and varies with Oh and We, indicating its connection to the splashing of minor droplets, which is also an outcome of inertia, viscosity, and surface tension. Moreover, the onset of droplet splashing is generally insensitive to δ. Based on that, a correlation between the splashing limit and the impingement angle is established and shows good agreement with numerical results at moderate impingement angles.