Bubble size and foamability: Role of surfactants and hydrodynamic conditions

The primary objective of this review is to consolidate our current understanding of the factors controlling the foamability of surfactant solutions under hydrodynamic conditions realized in various laboratory tests. In particular, two regimes of foam generation are considered: at low surfactant concentrations where the coalescence between the bubbles plays a crucial role, and a high surfactant concentration range where the hydrodynamic conditions are much more important for the final outcome of foaming. The review discusses the role of surfactant concentration, dynamic surface coverage, and surface forces acting between film surfaces for the foam generated in the surfactant-poor regime. Additionally, the interplay between the hydrodynamic conditions and the viscosity of the formed foams in the surfactant-rich regime is also discussed.