HYDRODYNAMICS AND ACOUSTICS OF DROP IMPACT

Synchronous macrophotography, high-speed video filming, hydro-acoustic and air acoustic data were used to investigate physical processes initiated by the impact of free falling droplet on the surface of a fluid at rest. Planning of the experiment was carried out on the basis of fundamental equations. In the experiments, the droplets of colored water, milk, mineral oil, and seed oil fell in pure or colored water. Emphasis was placed on recording the pattern of the drop material spreading over the surface of the targeted fluid and a fine structure of acoustic signals. Traces of impacting droplets (sprays) were for the first time recorded on the surface of a submerged drop. The droplet material is concentrated on the surfaces of the cavity and crown in short thin fibers forming a regular linear or cellular patterns. The cell rows are ordered in the form of echelons separated by circular boundaries. A high frequency impact pulse and delayed secondary ones were recognized both in hydrophone and microphone signals. Generation of sound are operated by processes of formation, separations and oscillation of gas cavities with irregular forms.