Coalescence Patterns of Homogeneous Drops of Solutions and Suspensions of Chemically Neutral and Reacting Media

Abstract

The evolution of the fine structure of the momentum, matter, and energy transfer pattern for а freely falling drop of pure liquid, a homogeneous solution, and suspensions of nanoparticles upon its coalescence with a stationary target liquid has been traced. A system of fundamental equations of heterogeneous fluid mechanics, including the equations of state for the Gibbs potential and density, is selected as the scientific basis of experimental methodology. High-speed video recording with multipoint illumination has made it possible to identify several flow regimes, the structure of which is determined by the ratio of the total energy components of the drop. At a low contact velocity, when the kinetic energy of the drop is lower than the potential surface energy (PSE), in the intrusive mode, the drop smoothly flows into the depth of the liquid and transforms into a vortex ring. In the intermediate mode, the drop hangs on the surface and partially coalesces, ejecting the remainder into the air. In the impact mode, the drop loses its continuity and disintegrates into separate trickles flowing along the contact surface and piercing the bottom of the cavity. The trickles leave behind colored filaments that form linear and reticular structures. The coalescence of chemically reacting liquids and nanoparticle suspensions is also considered.