Geometry, Dynamics, and Acoustics of Drop Flows in Gravitational and Electrostatic Fields

Abstract

This paper analyzes the flow geometry, mass transfer of free-falling drops coalescing with a transparent target liquid, and the generation of acoustic packets in gravitational and electrostatic fields. Parameterization is based on a system of fundamental equations (SFE) for the mechanics of heterogeneous liquids, including equations of state for density and Gibbs potential. State-of-the-art experimental techniques are described. The analysis includes flow structures across varying density ratios, kinetic energy, and potential surface energy (PSE) of the drop. Several coalescence regimes are identified, including intrusive, impact (with drop disintegration into filaments), and an intermediate regime of levitation and rebound. In the intrusive regime, a smoothly inflowing drop forms a coherent volume. In the impact regime, ligaments—thin filaments containing matter from the two media—form at the impact spot. These filaments pierce the base and walls of the cavity, spread across the liquid surface, and are ejected into the air. Fibrous traces of ligaments form ruled and reticular structures on the surface and within the bulk of the liquid. In the intermediate regime, a drop may hover, make contact, partially coalesce, and then rebound with m ass loss. The evolution of gas cavities and bubbles is traced, and the parameters of acoustic packets in external fields are determined. The study emphasizes the need to account for various energy transfer mechanisms—both macroscopic (flows, waves, vortices) and microscopic (dissipative and conversive)—when describing the dynamics and acoustics of drop flows.