Experimental Study of the Effect of the Surfactant on the Single Bubble Rising in Stagnant Surfactant Solutions and a Mathematical Model for the Bubble Motion

Bubble behavior has a significant effect on the gas-liquid mass transfer in bubbly flows. In this study, the bubble rising velocity and bubble shape in ultrapure water and surfactant solutions are experimentally measured by high-speed photography. The bubble velocity decreases and the bubble shape tends to be spherical due to the presence of the surfactant. As the bubble diameter increases, the rising velocity increases and bubble deformation becomes significant. The variations of the bubble velocity and shape exhibit different features under different surfactant concentrations. The effect of surface contamination on the bubble velocity is analyzed. Based on the stagnant cap model, a mathematical model coupling the surfactant adsorption and desorption on the bubble surface and the dynamic bubble motion in stagnant solutions is further proposed. The proposed model is validated by comparing the calculated bubble velocities with experimental values.