Coalescence of liquid drops with free surfaces

The present study investigates the coalescence phenomenon of pendant drops in the presence of liquid free surfaces. The experimental setup is composed of a glass cell placed on a lab-jack and a needle connected to a micro-syringe which controls the volume of the droplet. We acquired videos over the dynamics of the phenomenon with a fast CMOS camera attached to an objective with a microscopic magnification. Depending on the fluids properties (in our case water, respectively solutions of glycerin in water) and the distance between the needle and the fluid surface, the coalescence phenomenon evolves in different manners. The study emphasizes the effect of viscosity over the dynamics of the droplet and on the evolution of the capillary bridge between the needle and the free surface.