Multi-Frequency Sonoreactor Characterisation in the Frequency Domain Using a Semi-Empirical Bubbly Liquid Model

Abstract

Recently, multi-frequency systems were reported to improve performance in power ultrasound applications. In line with this, digital prototyping of multi-frequency sonoreactors also started gaining interest. However, conventional time-domain simulations used to consider the multiple frequencies led to many challenges and limitations. In this study, a multi-frequency sonoreactor was characterised using frequency domain simulations in 2-D. Using Parseval’s theorem, the root-mean-squared acoustic pressure was compared against experimental validation results using sonochemiluminescence (SCL). A semi-empirical, modified Commander and Prosperetti model was used to describe the bubbly-liquid effects in the sonoreactor. The studied system consists of a hexagonal 16.5 L sonoreactor capable of operating at 28, 40 and 70 kHz. Four frequency combinations were studied: 28-40, 28-70, 40-70 and 28-40-70 kHz. The root-mean-squared acoustic pressure fields showed good qualitative agreement with SCL results in terms of antinode predictions. The empirical phase speed calculated from SCL measurements was found to be useful in terms of circumventing uncertainties in bubble parameter specifications. Case study results have also shown that the root-mean-square acoustic pressure is a promising tool to characterise the cavitation potential in the multi-frequency sonoreactor.