(A) liquid drop impact on a liquid pool with an inclined bottom substrate

Abstract

We investigated the evolution of liquid interface deformation when a vertically falling droplet impacts to a liquid pool with an inclined bottom wall. We observed that initially nearly hemispherical like cavity was formed, then reversal of asymmetrical cavity was observed. Eventually, a tilting jet was measured. In order to conduct systematic experiments, substrate angle, depth, droplet diameter, impact velocity, surface tension, and viscosity were controlled. We found out that the hemispheric cavity development, which is driven by inertia, is analogous to the impact problems in a deep bath. Furthermore, when the cavity retracts, it shows an oblique conical shape, which is due to the different wave propagation mechanism depending on the bath depth, i.e. a relatively shallow and deep bath. Finally, we provided a theoretic model to predict the jet inclination angle from the competition of the two different wave propagations. Additionally, we qualitatively studied the viscosity effect on the impact process. Furthermore, we suppressed the inclination of the jet by adding porosity on the bottom wall.