Effects of Film Thickness and Impingement Angle on Drop Impact onto a Liquid Film

Abstract

Two-dimensional interface tracking simulations and photographic experiments were carried out to investigate the effects of film thickness and impingement angle on the splashing event during single-drop impact onto a plane liquid surface. For sufficiently small values of liquid film depth, liquid originally included in the inner region of liquid crown was not transported to the outer region. As a result, the pressure rise at the impact neck became significant, a thin liquid crown was formed, and the crown wall was broken into many secondary drops. Numerical results showed that the pressure rise induced on the bottom wall by drop impact is significantly mitigated if the impacted wall is covered with the liquid film whose thickness is comparable to the primary drop size. With respect to the effect of impingement angle, pressure rise in liquid was equally dependent on the normal and tangential components of impact velocity for slightly and moderately oblique impacts; however, the pressure rise was mitigated for very oblique impacts.