Decay of large underwater bubble oscillations
The Journal of the Acoustical Society of America
|June 30, 2000
Summary
Large underwater bubbles decay faster than expected due to energy transfer to surface waves, causing turbulence. This mechanism explains the high decay rates observed in these large bubbles.
Area of Science:
- Fluid dynamics
- Acoustics
- Bubble dynamics
Background:
- Microbubble decay mechanisms (viscous, thermal, radiative) do not explain large bubble decay rates.
- Large bubbles exhibit significantly higher decay rates than predicted by existing models.
Purpose of the Study:
- To investigate the mechanisms behind the rapid decay of large underwater bubbles.
- To propose a new model explaining the observed high decay rates.
Main Methods:
- Analysis of pressure-time series from breathing-mode oscillations of large bubbles.
- Modeling energy transfer to large-amplitude surface capillary waves.
- Application of eddy viscosity from mixing-length theory.
Main Results:
- Energy transfer to shape oscillations can drive external fluid motions.
- These motions can excite turbulent instabilities, leading to rapid decay.
- The proposed mechanism involving surface capillary waves and turbulence credibly explains observed decay rates.
Conclusions:
- Subharmonic resonance of surface capillary waves is a key factor in large bubble decay.
- Turbulent instabilities driven by bubble shape oscillations are responsible for high decay rates.
- The eddy viscosity model provides a viable explanation for the rapid dissipation of energy in large bubbles.
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