Observations of the coalescence of miscible drops

Abstract

The coalescence motions of two fluid liquid masses were imaged and observed with a PIV camera. The effects of large difference of surface tension and viscosity between liquid masses on the coalescence motions were explored. Marangoni waves were observed in the coalescence of a water drop with a pool of ethanol and the wave was shown to be self-similar scaled with time to the 3/2 power. When high viscosity difference applied between the liquid masses, capillary wave dampened and a sharp corner characterizes the region where two fluids meet. Moreover, limited experiments were carried out with surfactants solutions coalescing with pure water drops.