Shock Acoustic Emission upon Collision of a Droplet of Variable Shape with the Water Surface

Abstract

Sound emission at the stage of supersonic expansion of a contact spot upon collision of a droplet with the water surface is discussed in theoretical and experimental setting. Measurements of acoustic signals were carried out with simultaneous video recording of the falling drop. The shock pulse amplitude does not depend on the shape of the underwater drop segment; it is determined only by the impact velocity and current geometric parameters of the surface segment, of which the shape is fixed in the video frame that is last one before impact. The shape envelope is approximated by continuous function that is used to simulate the supersonic expansion of the contact spot and calculate the shock pulse amplitude. Closeness of the calculated and experimental data confirms the stability of the shape of the surface drop segment during the shock pulse emission.