Effects of adsorbed films on gas bubble radial oscillations

Adsorption films’ mechanical properties are discussed. With regard to a problem of bubble oscillations in a surfactant solution, dynamical boundary conditions at the bubble wall are modified by including a new term to account for a normal force component caused by dilational elasticity of an adsorbed film. Consequently, the Rayleigh–Plesset equation acquires a term which affects the restoring force of bubble oscillations. A linearized theory (for small-magnitude oscillations) is developed which shows that the film dilational elasticity induces a change in the mean radius and a shift in the natural frequency of bubble oscillations. These effects become extremely important when a capillary component 2σ/R0 accounts for at least 20% of the total pressure inside the bubble.