Bubbles in liquids are part of many industrial applications. Liquids usually contain surfactants that adsorb on the surface of the bubbles and significantly influence their behavior. This work investigates the damping effect of surfactants on bubble surface deformation in two experiments. A high-speed camera is used to observe the controlled oscillations of the bubble and the rebound of the bubble from the solid wall. These experiments are performed in pure water and aqueous solutions of five different surfactants. The recorded videos allow comparison of the frequencies and decay times of the induced oscillations, as well as the degree of attenuation of the rebound of the bubble from the solid wall.
It was found that the surface elasticity of the bubble plays a key role and that there is a universal relationship between the energy dissipation during bubble deformation and the surfactant concentration on its surface. The deformation damping time decreases rapidly with increasing surfactant concentration, reaches a minimum, and stabilizes at a final value at high concentrations. In both cases studied, it is necessary to reach approximately the same optimum value of surface elasticity (4 mN/m) for the maximum damping of interfacial deformations. In addition, the rebound of the bubble from the wall is very sensitive to the presence of even a trace amount of surfactant.
- Vobecká L., Orvalho S., Zedníková M., Vejražka J., Tihon J.*: Damping effect of surfactants on induced bubble shape deformations. Phys. Fluids 2023, 35(12), 122120. doi: 10.1063/5.0174954