Classification of the major nonlinear regimes of oscillations, oscillation properties, and mechanisms of wave energy dissipation in the nonlinear oscillations of coated and uncoated bubbles

<jats:p>Acoustic waves are dissipated when they pass through bubbly media. Dissipation by bubbles takes place through thermal damping (Td), radiation damping (Rd), and damping due to the friction of the liquid (Ld) and friction of the coating (Cd). Knowledge of the contributions of Td, Rd, Ld, and Cd during nonlinear bubble oscillations will help in optimizing bubble and ultrasound exposure parameters for the relevant applications by maximizing a desirable outcome or oscillation pattern. In this work, we investigate the mechanisms of dissipation in bubble oscillations and their contribution to the total damping (Wtotal) in various nonlinear regimes. By using a bifurcation analysis, we have classified nonlinear dynamics of bubbles that are sonicated with their third superharmonic (SuH) and second SuH resonance frequency (fr), pressure dependent resonance frequency (PDfr), fr, subharmonic (SH) resonance (fsh = 2fr), pressure dependent SH resonance (PDfsh), and 1/3 order SH resonance, which are important exposure ranges for various applications. The corresponding Td, Rd, Ld, Cd, Wtotal, scattering to dissipation ratio, maximum wall velocity, and maximum backscattered pressure from non-destructive oscillations of bubbles were calculated and analyzed using the bifurcation diagrams. Universal ultrasound exposure parameter ranges are revealed in which a particular non-destructive bubble related phenomenon (e.g., wall velocity) is enhanced. The enhanced bubble activity is then linked to relevant ultrasound applications. This paper represents the first comprehensive analysis of the nonlinear oscillations regimes, the corresponding damping mechanisms, and the bubble related phenomena.</jats:p>