Perturbation of a radially oscillating single-bubble by a micron-sized object

Area of Science:

• Acoustics
• Bubble Dynamics
• Sonoluminescence

Background:

• Acoustic monitoring of single oscillating bubbles in levitation cells provides insights into bubble behavior.
• Piezo-ceramic microphones capture acoustic signals from bubble oscillations.

Purpose of the Study:

• To investigate the correlation between acoustic signals and bubble stability/existence.
• To determine if acoustic monitoring can detect bubble disappearance and external perturbations.

Main Methods:

• Acoustic monitoring of a single oscillating bubble using a piezo-ceramic microphone.
• Analysis of filtered acoustic signals and their harmonic content.
• Perturbation of stable bubbles with a micron-sized fiber and subsequent acoustic and visual analysis.

Main Results:

• Harmonic content increases significantly when a bubble transitions to the upper sonoluminescence regime, indicating pure argon composition.
• Bubble disappearance is marked by a sharp drop in harmonic content.
• Acoustic detection of bubble disappearance shows a delay due to decaying cell modes.
• Bubble instability and disappearance are triggered when a fiber approaches within 3-4 times the bubble's maximal radius.

Conclusions:

• Acoustic monitoring, particularly harmonic content analysis, is a reliable method for assessing bubble stability and detecting disappearance.
• The acoustic method can detect perturbations by foreign objects, enabling early warning and imaging.
• The observed delay in acoustic detection is attributed to the resonant modes of the levitation cell.