Mass and heat transfer in audible sound driven bubbles

Area of Science:

• Acoustics and Fluid Dynamics
• Physical Chemistry
• Computational Modeling

Background:

• Sonoluminescence and sonochemistry research predominantly uses frequencies above 20 kHz.
• Mathematical models for acoustically-driven bubble dynamics are scarce in the audible frequency range (below 20 kHz).

Purpose of the Study:

• To develop and validate a hybrid modeling approach for inertially collapsing bubbles driven by audible sound.
• To assess the accuracy of reduced-order models at lower acoustic frequencies compared to a more rigorous advection-diffusion model.

Main Methods:

• A novel hybrid model combining advection-diffusion and boundary layer approaches was developed.
• Phase-change, mass, and heat transfer in bubbles were predicted.
• Validation was performed against experimental data from ultra-high-speed videos of bubble dynamics at 17.8 kHz.

Main Results:

• The boundary layer model shows significant deviations from the advection-diffusion model at audible frequencies (e.g., 17.8 kHz).
• Reduced-order models overpredict bubble size and trapped vapor while underpredicting temperature and pressure at lower frequencies.
• Deviations stem from inaccurate boundary layer thickness estimation due to time-scale competition between diffusion and bubble wall motion.

Conclusions:

• Existing reduced-order models developed for ultrasonic frequencies are not suitable for the audible range.
• Further research into bubble dynamics modeling within the audible frequency spectrum is essential.
• The developed hybrid model offers a more accurate approach for studying audible sound-induced bubble behavior.