Instantaneous deformation characteristics of a single bubble in immiscible fluids

The passage of a rising bubble through immiscible fluids is encountered in bath smelting. In order to investigate characteristics of bubble deformation in immiscible fluids, the bubble shape change at the interface and the relationship between the bubble aspect ratio (E) and dimensionless number of forces were obtained. A three-dimensional model was established, and the free-floating behavior of a single bubble in immiscible fluids was numerically simulated by phase-field method. The simulation results are in good agreement with experimental results. The results indicate that when the bubble passes through the interface, the bubble shape is divided into four types in turn: “pear”, inverted “pear”, “convex” and “droplet” shape. In the lower liquid, the relationship of E to Weber number (We), Tadaki number (Ta), and Reynolds number (Re) is distributed between two intersecting lines. The relationship of E to Eötvös number (Eo), a dimensionless group, and Galilei number (Ga) is distributed near the lines with slopes of − 3.325 × 10^–5, − 0.0855, and − 8.73 × 10^–4, respectively. In the upper liquid, the relationship of E to We, Ta, and Re is distributed between two parallel lines. Compared with gravity, the inertial force plays a leading role in the bubble shape in the lower and upper liquid. Compared with the viscous force, the surface tension dominates the bubble shape in the lower liquid.