Finite amplitude wave propagation through bubbly fluids

TL;DR

This paper investigates how finite amplitude acoustic waves propagate through bubbly fluids, revealing that low frequency waves persist and are transmitted via bubble collapse, with wave speed decreasing as bubble concentration increases.

Contribution

It introduces a model connecting linear and shock wave regimes in bubbly media using a Mach number based on bubble collapse velocity.

Findings

High frequency components are quickly attenuated in bubbly media.

Low frequency waves persist and are transmitted through bubble collapse.

Wave speed decreases with increasing bubble void fraction.

Abstract

The existence of only a few bubbles could drastically reduce the acoustic wave speed in a liquid. Wood's equation models the linear sound speed, while the speed of an ideal shock waves is derived as a function of the pressure ratio across the shock. The common finite amplitude waves lie, however, in between these limits. We show that in a bubbly medium, the high frequency components of finite amplitude waves are attenuated and dissipate quickly, but a low frequency part remains. This wave is then transmitted by the collapse of the bubbles and its speed decreases with increasing void fraction. We demonstrate that the linear and the shock wave regimes can be smoothly connected through a Mach number based on the collapse velocity of the bubbles.