Evolution of the Fine Structure of the Matter Distribution of a Free-Falling Droplet in Mixing Liquids

Abstract

In this paper we study the evolution of the matter distribution pattern of ink droplets falling freely into calm water and forming a cumulative back jet by tracing with high-speed video recording. In the phase of primary contact and immersion, the matter of a drop merging with the receiving liquid is distributed in the form of fine fibers forming a regular striped pattern on the surface of the growing crown and a net pattern consisting of three-, four-, and pentagonal cells at the cavity bottom. The fibrous distributions of the colored liquid remain at all subsequent stages of the flow evolution until the formation of a vortex cascade. Then the picture is blurred due to molecular diffusion in a practically quiescent liquid. The formation of a discrete (fibrous) pattern of the drop matter distribution is associated with the compactness of the region of release of the available potential surface energy during the confluence of liquids that initiates a fast movement of a thin layer. Subsequent fiber preservation is provided by the slowness of molecular diffusion.