Bubble formation from a submerged orifice in a thin liquid layer: Detachment and bursting

Abstract

Bubbles dispersed in thin liquid layers are ubiquitous and play important roles in the heat and mass transfer in nature and industrial processes including the energy, chemical, and biology engineering; thus, understanding the dynamics of bubbles confined in a liquid layer remains an important topic in multiphase flows. Here, we report the dynamics of bubble formation from a submerged orifice in a thin liquid layer with a thickness comparable to the bubble size. First, four flow regimes, detachment, jetting bursting, non-jetting bursting, and hole-opened bursting, are observed experimentally and their typical features are analyzed. Then, the evolutions of bubble size at different regimes are studied, and a quasi-static force model is proposed to predict the bubble size, which agrees well with the experimental results. We demonstrate the role of the capillary force exerted by the liquid film in the bubble cap and bubble geometry confined in the liquid layer in modulating the bubble size. Finally, a regime map regarding the liquid layer thickness and surface tension is provided and the criteria between different regimes are discussed based on the bubble geometry analysis and energy balance. Our experimental investigation and theoretical analysis provide insights into the formation and bursting dynamics of bubbles confined in a liquid layer.