Affiliation:
1. Ishlinsky Institute for Problems in Mechanics, Russian Academy of Sciences
Abstract
The paper studies acoustic signals in two modes of merging with water in a freely falling water droplet by the matched optical and acoustic methods. Only the primary sound packet was observed in the intrusive mode at the low drop speed, when the cavity was formed with a delay in the colored wake of the inflowing liquid. Experiments demonstrated the drop speed influence on the primary signal parameters. At the high droplet speed, the cavity started to form from the moment of the initial contact. The flow pattern became more complicated, the droplet substance was distributed over the emerged cavity surface and the grown crown in the form of separate fibers forming the line and mesh structures. The falling section of the primary acoustic signal was formed by a group of pulses with the complex spectral composition. Further, one or more low-frequency sound packets were registered after the pause. Spectral portrait of the secondary packets was related to the shape of the detached gas cavity. Smooth axisymmetric cavity was radiating the monochromatic packet. The complex-shaped cavity was transforming into a gas bubble and emitting the multi-frequency signal. Duration and amplitude of the secondary sound signals were depending on the transformation rate of the separated gas cavity into a smooth spheroidal bubble. The acoustic signal parameters were changing nonmonotonically with increasing velocity of the merging drop
Funder
Russian Science Foundation
Publisher
Bauman Moscow State Technical University
Subject
General Physics and Astronomy,General Engineering,General Mathematics,General Chemistry,General Computer Science