Study of the bubble collapse mechanism and its influencing factors on stability under ultra-low surface tension

Abstract In this paper, a foam stability model was established to analyze the flow rate, pressure, and gas–liquid phase distribution of the foam during the crushing process, and the evaluation method of foam stability was improved. The results show that the collapsing process of foam is mainly affected by the release of energy inside the foam, and the pressure inside the foam is higher. Before the collapsing of the foam, the velocity of the liquid film position fluctuates and, with the increase in time, the amplitude of the velocity fluctuation increases. When the surface energy between the gas–liquid phases is less than the kinetic energy inside the gas, the bubble collapses and the energy inside the bubble is released. The method of evaluating foam stability was further determined. The stability of foam was analyzed by studying the volume fraction of liquid phase at the location of the foam liquid membrane. For a single bubble, the larger the size of the bubble and the thicker the thickness of the liquid film, the more stable the foam. The density and viscosity of the liquid phase have relatively little effect on foam stability. For the same surfactant, when the surfactant concentration is lower than the critical micelle concentration, the higher the surfactant concentration in the liquid phase, the lower the surface tension between the liquid phase and the gas phase, and the better the foam stability. For different surfactants, the lower the surface tension, the stronger the foaming.