Void fraction, number density of acoustic cavitation bubbles, and acoustic frequency: A numerical investigation

The present paper consists of a numerical study attempting to characterize the bubble population within a sonochemical reactor through modeling and simulating the number density of bubbles and the void fraction. In a first step, both previous parameters were estimated under 1.52 bar and various acoustic frequencies ranging from 20 to 1000 kHz in function of normalized time. The results showed that the average number density of bubbles, varying within the interval 2.810⁴-1.4 × 10¹² bubbles dm^-3, follows a clear monotonous evolving trend as the frequency increases, while the average void fraction, comprised between 9.05 × 10^-5 and 1.95 × 10^-4, demonstrates no dependency of acoustic conditions. In a second step, an energy analysis was performed at microscopic and macroscopic scales, which led the authors to figure out that the evolution of the number density of bubbles in function of acoustic frequency is mainly governed by the energy required to maintain oscillating the single cavitation bubble.