(234q) Impact Forces of Inertia-Driven Liquid Drops

Liquid drop impacts on solid surface are ubiquitous relevant to many important natural and industrial processes. Although the dynamics of liquid-drop impacts have been extensively studied by high-speed photography, comparatively fewer experiments have been conducted to explore the impact forces induced by liquid drops. Particularly, the temporal variation of impact forces during impact has not been systematically investigated. Here, by synchronizing high-speed imaging with fast force measurements, we investigate the detailed temporal variation of impact forces induced by inertia–driven liquid-drop impacts. Our experiments on the rise of impact forces at early times unambiguously demonstrate the existence of self-similar inertial fronts during the initial impact of liquid drops. Moreover, we systematically study how the intrinsic properties of drops affect impact forces. We find that, for low-viscosity liquid drops, the temporal variation of impact forces is highly asymmetric. As viscosity increases, impact forces become more symmetric approaching those induced by the impact of solid spheres. Our study reveals an important yet unexplored aspect of drop impacts and illustrates the transition between liquid-drop and solid-sphere impacts from the perspective of impact forces.