Permeability of aqueous foams.

Area of Science:

• Fluid Dynamics
• Materials Science
• Colloid and Surface Chemistry

Background:

• Aqueous foams are ubiquitous in industrial and natural processes.
• Understanding foam drainage is critical for controlling foam behavior and stability.
• Existing models often fail to accurately describe wet foam drainage.

Purpose of the Study:

• To reconcile disparate experimental data on forced foam drainage.
• To evaluate the validity of current foam drainage models.
• To propose improved models for wet foam conditions.

Main Methods:

• Performing forced-drainage experiments on aqueous foams.
• Comparing experimental results with existing literature data.
• Analyzing foam behavior as a function of liquid fraction and dimensionless permeability.

Main Results:

• Dimensionless foam permeability plotted against liquid fraction provides a unifying coordinate system for experimental data.
• Most published data represent relatively wet foams (liquid fraction ~0.1).
• Existing models, often based on dry foam assumptions, have limited applicability.

Conclusions:

• A new framework using liquid fraction and dimensionless permeability accurately describes foam drainage.
• Extensions to existing models are proposed for the wet foam regime.
• The Boussinesq number emerges as a key parameter for understanding forced drainage in foams when geometry is properly considered.