Visualization and optimization of cavitation activity at a solid surface in high frequency ultrasound fields

Area of Science:

• Physical Chemistry
• Acoustics
• Materials Science

Background:

• High frequency ultrasound is increasingly used in heterogeneous reactions.
• Understanding cavitation bubble distribution on solid surfaces is crucial but limited.
• This knowledge gap impedes controllable surface sono-chemical reactions.

Purpose of the Study:

• To optimize the spatial distribution of cavitation bubbles at a solid sample surface.
• To investigate the influence of sample properties and orientation on cavitation.
• To provide insights for controllable surface sono-chemical processes.

Main Methods:

• Experiments utilizing sonoluminescence and sonochemiluminescence imaging.
• Testing at three distinct ultrasound frequencies (580, 860, and 1142 kHz).
• Numerical simulations using the Finite Element Method (FEM) to model acoustic fields.

Main Results:

• Sample position, orientation, and material properties significantly affect cavitation bubble distribution.
• Solid sample interactions (reflection, absorption) modify the acoustic field.
• FEM simulations showed good agreement with experimental luminescent zones and predicted high acoustic pressure areas.
• A nearly vertical sample inclination relative to the incident wave achieved homogeneous cavitation coverage.

Conclusions:

• Acoustic field modification by solid samples is a key factor in cavitation distribution.
• Sample orientation is a critical parameter for controlling cavitation.
• Vertical sample inclination is optimal for achieving homogeneous cavitation coverage on surfaces for enhanced sono-chemical reactions.