Numerical Characterization of Acoustic Cavitation Bubbles with Respect to the Bubble Size Distribution at Equilibrium

Kaouther Kerboua,Abdulaziz Alghyamah,Oualid Hamdaoui

doi:10.3390/pr9091546

Abstract

In addition to bubble number density, bubble size distribution is an important population parameter governing the activity of acoustic cavitation bubbles. In the present paper, an iterative numerical method for equilibrium size distribution is proposed and combined to a model for bubble counting, in order to approach the number density within a population of acoustic cavitation bubbles of inhomogeneous sizing, hence the sonochemical activity of the inhomogeneous population based on discretization into homogenous groups. The composition of the inhomogeneous population is analyzed based on cavitation dynamics and shape stability at 300 kHz and 0.761 W/cm2 within the ambient radii interval ranging from 1 to 5 µm. Unstable oscillation is observed starting from a radius of 2.5 µm. Results are presented in terms of number probability, number density, and volume probability within the population of acoustic cavitation bubbles. The most probable group having an equilibrium radius of 3 µm demonstrated a probability in terms of number density of 27%. In terms of contribution to the void, the sub-population of 4 µm plays a major role with a fraction of 24%. Comparisons are also performed with the homogenous population case both in terms of number density of bubbles and sonochemical production of HO•,HO2•, and H• under an oxygen atmosphere.

Highlights

IntroductionAcoustic cavitation bubble is a complex dynamical phenomenon occurring when the liquid phase is submitted to an acoustic field in the ultrasound range with sufficient amplitude [1]
A single acoustic cavitation bubble from each sub-population is dynamically studied under the effect of an acoustic field of 300 kHz and 0.761 W/cm2
The sub-population having a representative ambient radius of 1 μm is composed of stable acoustic cavitation bubbles, the oscillation of the bubble wall is integrally repeated from one acoustic cycle to the other

Summary

Introduction

Acoustic cavitation bubble is a complex dynamical phenomenon occurring when the liquid phase is submitted to an acoustic field in the ultrasound range with sufficient amplitude [1]. The phenomenon has been widely investigated for its physical [2] and chemical consequences [3]. Most of the numerical works that investigated the acoustic cavitation phenomenon were limited in scale to the single acoustic cavitation bubble [11,12,13,14]. Some researcher attempted to numerically explore the multibubble dimension by investigating parameters such as the number density of bubbles [15,16,17], bubble–bubble interaction [18,19,20], and bubble size distribution [21]. Some examples of multibubble approaches are found in the studies of Yasui [22], Colonius et al [23] and

Methods

Results

Conclusion