Manipulation mechanisms of bubble aggregation and evolution in inertial cavitation fields

Area of Science:

• Acoustics
• Fluid Dynamics
• Nonlinear Systems

Background:

• Bubble clusters form under acoustic fields.
• Their behavior is influenced by standing waves and acoustic pressure.
• Understanding cluster dynamics is crucial for cavitation manipulation.

Purpose of the Study:

• To investigate the evolution and properties of spherical bubble clusters.
• To explore the attractive effects of bubble clusters on surrounding bubbles.
• To provide a theoretical model for manipulating cavitation fields, especially at high hydrostatic pressures.

Main Methods:

• Observation of bubble clusters at 28 kHz and 40 kHz.
• Development of a theoretical model considering high hydrostatic pressure.
• Analysis of equilibrium radii distribution and key interaction factors.

Main Results:

• Bubble clusters are dense at antinodes and sparse elsewhere, showing period-doubling bifurcation.
• Complex fragmentation and coalescence within clusters suggest a bubble transportation cycle.
• High hydrostatic pressure allows for denser clusters attracting bubbles within a 2 mm radius.

Conclusions:

• Bubble cluster density and behavior are governed by acoustic pressure, hydrostatic pressure, and acoustic frequency.
• Theoretical predictions support optimizing cavitation behavior in bubble populations at high hydrostatic pressures.
• The study offers insights into bubble transportation and interaction mechanisms within clusters.