Localization in an acoustic cavitation cloud

TL;DR

This paper combines theoretical modeling and experiments to study how sound waves localize or are forbidden in cavitation clouds with bubbles of specific sizes, revealing size-dependent spectral gaps.

Contribution

It introduces a combined nonlinear acoustic model and experimental validation for sound localization and forbidden bands in cavitation clouds with specific bubble sizes.

Findings

Spectral gaps correspond to sound localization for 100 μm bubbles.

Forbidden sound bands are observed for bubbles with 120 μm radius.

Experimental results match theoretical predictions in soda water.

Abstract

Using a nonlinear sound wave equation for a bubbly liquid in conjunction with an equation for bubble pulsation, we predict and experimentally demonstrate the appearance of a gap in the frequency spectrum of a sound wave propagating in a cavitation cloud comprising bubbles. For bubbles with an ambient radius of 100 {\mu}m, the calculations revealed that this gap corresponds to the phenomenon of sound wave localization. For bubbles with an ambient radius of 120 {\mu}m, this spectral gap relates to a forbidden band of the sound wave. In the experiment, we observed the predicted gap in the frequency spectrum in soda water; however, in tap water, no spectral gap was present because the bubbles were much smaller than 100 {\mu}m.