Sound of Interfacial Flows: Unraveling the Forces Shaping Fast Capillary Flows using their Acoustic Signature

TL;DR

This paper explores how the sounds produced by rapid interfacial flows, like bursting soap bubbles, reveal detailed information about the underlying physical forces and dynamics, providing a new way to analyze such phenomena acoustically.

Contribution

It introduces a novel approach linking acoustic signatures to interfacial hydrodynamics, revealing the influence of capillary forces and surfactant dynamics on sound emission.

Findings

Acoustic signals encode information about capillary forces.

Sound analysis complements ultra-fast imaging of flows.

Acoustic signatures can reveal out-of-equilibrium surfactant behavior.

Abstract

Many familiar events feature a distinctive sound: paper crumpling or tearing, squeaking doors, drumming rain or boiling water. Such characteristic sounds actually carry a profusion of informations about the fleeting physical processes at the root of acoustic emission, which appears appealing especially in situations precluding direct or in-situ measurements, such as e.g. the rupture of micron-thick liquid sheet. Here we report on such a link between fast interfacial hydrodynamics and sound. The acoustic emission of a bursting soap bubble is captured by means of antennae and deciphered with the conceptual framework of aeroacoustics. This reveals that capillary forces, thin-film hydrodynamics, but also out-of-equilibrium surfactants dynamics all shape the capillary burst sound. Whereas ultra-fast imagery only captures the shapes of flows, the acoustic signature radiated by hydrodynamical forces offers a timely complement for it allows a direct experimental access to these dynamical quantities.