Multiple drop impact onto a dry solid substrate

The impact of multiple drops on a dry substrate is studied experimentally and theoretically, as a preliminary model for relatively dense sprays. In the experiments the drop diameter, the impact velocity, the time interval between the impact of two drops, and the distance between the impacting drops were controlled. The shape of the liquid film formed on the substrate, the interface between the two drops, and the shape of the uprising sheets were observed using high-speed photography. In the theoretical model, the surface tension, wettability, viscosity, gravity, and inertia were taken into account. The agreement between the experiments and the theory is rather good considering that no adjustable parameters are used. (C) 2002 Elsevier Science (USA).