Ripening of a draining foam bubble.

Area of Science:

• Colloid and Surface Science
• Fluid Dynamics
• Materials Science

Background:

• Ostwald ripening is a key process in foam coarsening.
• Existing models often assume constant film thickness, which may not hold under dynamic conditions.

Purpose of the Study:

• To investigate the Ostwald ripening dynamics of a single foam bubble under controlled liquid flow.
• To determine the relationship between film thickness and liquid flow rate.
• To develop a more accurate model for bubble growth during ripening.

Main Methods:

• A single foam bubble was subjected to forced Ostwald ripening.
• Constant liquid flow was supplied to a Plateau border.
• Bubble size and film thickness were measured experimentally.
• A modified ripening model incorporating film thickness evolution was developed and tested.

Main Results:

• Ripening velocities were not accurately predicted by models assuming constant film thickness.
• Experimental measurements revealed that film thickness is dependent on the imposed liquid flow rate.
• The bubble growth rate was accurately predicted when the model explicitly included the measured film thickness evolution.

Conclusions:

• The assumption of constant film thickness is inadequate for describing Ostwald ripening under forced flow conditions.
• The developed model, accounting for dynamic film thickness, provides a better prediction of bubble growth.
• This approach may offer a new perspective for understanding the coarsening of draining foams.