Investigation of the 1/2 order subharmonic emissions of the period-2 oscillations of an ultrasonically excited bubble

work, through applying a comprehensive bifurcation analysis method, we study the nonlinear radial oscillations of the bubble oscillator. The frequency of the driving force is chosen as the linear resonance frequency (f(r)) and linear subharmonic (SH) resonance frequency (f(sh) = 2f(r)) of the bubble. Results show that, when the bubble is sonicated with 2f(r), period doubling is more likely to result in non-destructive oscillations. The evolution of the period-2 (P2) oscillations of the bubble makes the shape of a bowtie for bubbles with an initial diameter of 0.74 mu m and above. When f = 2f(r), the phase portrait of the P2 attractor is distinctly different from a P2 attractor when f = f(r), and subharmonic component of the backscattered pressure is maximum. When sonicated by 2f(r), due to lower oscillation amplitude and gentler bubble collapse, the bubble can sustain stable P2 oscillations for a longer duration and over a broader range of applied acoustic pressure. (C) 2020 Elsevier B.V. All rights reserved.