Dynamics of an oscillating bubble in a narrow gap

Area of Science:

• Fluid dynamics
• Microscale phenomena
• Optical physics

Background:

• Oscillating bubbles in confined geometries are crucial in various industrial and natural processes.
• Understanding bubble dynamics in narrow gaps is essential for applications like microfluidics and boiling heat transfer.
• Previous studies often simplified these systems as two-dimensional, neglecting complex three-dimensional effects.

Purpose of the Study:

• To investigate the complex dynamics of a single oscillating bubble within a narrow fluid-filled gap between parallel plates.
• To elucidate the mechanisms behind bubble expansion, collapse, and ring formation using advanced imaging techniques.
• To identify and characterize novel bubble collapse behaviors influenced by gap width and surface properties.

Main Methods:

• Utilized high-speed videography with two synchronized cameras for simultaneous side and front views of the bubble.
• Analyzed bubble expansion and collapse patterns, including the formation of concentric rings observed in front-view images.
• Examined bubble trajectory and deformation during collapse from side-view recordings, correlating with gap width variations.

Main Results:

• Observed distinct bubble expansion and collapse behaviors, including the formation of concentric dark and bright rings.
• Identified two types of bubble collapse: inward collapse at narrow gaps and splitting followed by wall collapse at wider gaps.
• Demonstrated that bubble dynamics are independent of plate surface hydrophobicity/hydrophilicity due to a persistent liquid film.

Conclusions:

• Bubble dynamics in narrow gaps are inherently three-dimensional, challenging quasi-two-dimensional assumptions.
• A previously unreported bubble splitting and collapse phenomenon was characterized, dependent on gap width.
• The presence of a liquid film negates surface wettability effects on bubble behavior in this confined system.