Foam coarsening in a yield stress fluid

Area of Science:

• Materials Science
• Fluid Dynamics
• Colloid Science

Background:

• Foam coarsening is driven by pressure differences between bubbles of varying sizes.
• Understanding foam stability is crucial for applications in food, cosmetics, and industrial processes.

Purpose of the Study:

• To investigate the effect of yield stress fluids on the coarsening dynamics of quasi-2D foams.
• To model the influence of continuous phase rheology, foam wetness, and confinement on foam structure and evolution.

Main Methods:

• Utilized quasi-2D foams composed of concentrated oil-in-water emulsions as model systems.
• Systematically varied the yield stress of the continuous phase, foam wetness, and confinement.
• Developed a model incorporating resisting pressure to explain observed phenomena.

Main Results:

• Increased yield stress significantly slowed foam coarsening and induced irreversible structural changes.
• The impact of continuous phase rheology was amplified in wetter or more confined foams.
• Observed highly heterogeneous bubble growth and organization, with a prevalence of smaller bubbles.

Conclusions:

• Yield stress is a critical parameter controlling foam coarsening and structural stability.
• The developed model effectively rationalizes the interplay between yield stress, wetness, and confinement in foam dynamics.