Capillary waves at microdroplet coalescence with a liquid layer

Abstract

The quickly damped capillary waves generated at coalescence of microdroplets (diameter of up to 100 µm), formed in a gas atmosphere at water vapor condensation, with the horizontal layer of water are studied experimentally. Evaporation takes place at intensive local heating of liquid from the substrate side. To visualize and measure the deformations, the Schlieren technique and high-speed video (up to 54000 f/s) are applied. The measured wave amplitude varies within 1-6 μm, and this is consistent with the magnitude of the surface energy of coalescing microdroplets. The waves are generated by the energy of droplet surface.