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Published on: May 9, 2021
Development and optimization of acoustic bubble structures at high frequencies.
Judy Lee1, Muthupandian Ashokkumar, Kyuichi Yasui
1National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimoshidami, Moriyama ku, Nagoya 463-8560, Japan. judy.lee@aist.go.jp
Ultrasonics Sonochemistry
|May 11, 2010
Summary
Visible bubbles can indicate active bubble structures at high ultrasound frequencies. Monitoring these visible bubbles helps infer active bubble development and understand acoustic wave propagation dynamics.
Area of Science:
- Acoustics
- Fluid Dynamics
- Bubble Dynamics
Background:
- High ultrasound frequencies pose challenges in capturing active bubble structures due to reduced timescales and bubble sizes.
- Understanding bubble behavior is crucial for applications involving acoustic waves.
Purpose of the Study:
- To demonstrate the association between visible bubble distribution and active bubble structures at high ultrasound frequencies.
- To infer the development of active bubbles by monitoring visible bubble formation.
- To investigate the factors affecting standing wave fields at varying ultrasound frequencies.
Main Methods:
- Analysis of still images showing the formation of visible bubble structures.
- Observation of bubble behavior and spatial distribution under different acoustic frequencies (168 kHz, 448 kHz, 726 kHz).
- Explanation of forces like acoustic streaming and traveling wave force influencing bubble movement.
Main Results:
- A strong standing wave field is observed at 168 kHz.
- At 448 kHz, coalesced bubbles attenuate acoustic pressure, weakening the standing wave field.
- At 726 kHz, acoustic streaming significantly disrupts the standing wave structure.
- Bubble movement towards the liquid surface is observed due to acoustic streaming and traveling wave forces.
- Disruption of standing wave structure can be minimized using specific pulse ON/OFF ratios.
Conclusions:
- Visible bubble distribution serves as an indicator for active bubble structures at high ultrasound frequencies.
- Acoustic wave propagation and standing wave field strength are significantly influenced by bubble coalescence and acoustic streaming.
- Optimized pulsing strategies can mitigate standing wave disruption.
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