Curvature singularity and film-skating during drop impact

TL;DR

This paper investigates the impact dynamics of a drop on a surface, revealing a curvature singularity, film skating due to surface tension, and proposing an instability mechanism for splashing, with implications for understanding fluid-surface interactions.

Contribution

It introduces an axisymmetric 3D model analyzing gas and liquid interactions during drop impact, highlighting singularity formation and film skating phenomena.

Findings

Finite time singularity leads to liquid contact on a circle.

Surface tension causes a thin jet to skate above the gas layer.

Air film thickness suggests eventual wetting of the surface.

Abstract

We study the influence of the surrounding gas in the dynamics of drop impact on a smooth surface. We use an axisymmetric 3D model for which both the gas and the liquid are incompressible; lubrication regime applies for the gas film dynamics and the liquid viscosity is neglected. In the absence of surface tension a finite time singularity whose properties are analysed is formed and the liquid touches the solid on a circle. When surface tension is taken into account, a thin jet emerges from the zone of impact, skating above a thin gas layer. The thickness of the air film underneath this jet is always smaller than the mean free path in the gas suggesting that the liquid film eventually wets the surface. We finally suggest an aerodynamical instability mechanism for the splash.