Discrete particle-volume of fluid simulations of a bubble plume rising through two immiscible liquids

Bubbles rising through immiscible liquids are commonly encountered in various applications, e.g., in the steel-making and refining process. In the present work, we have modeled a bubble plume rising through an oil–water interface using the combined discrete particle method and volume of fluid method. The relative contributions of different forces (inertial, gravitational, viscous, and interfacial tension), which govern the oil phase distribution and oil–water interface topology, are investigated by varying the liquid properties (density, viscosity, and interfacial tension) and operating conditions (thickness of oil layer, gas flow rate, and bubble size). We show that the interplay among gravitational, inertial, and interfacial tension forces governs the oil–water interface topology, while the viscous force exerted by an oil layer has a negligible influence. We identified four different interface topology regimes: (i) mildly deformed, (ii) partially deformed, (iii) fully exposed, and (iv) dispersed regime, and a corresponding regime map is proposed using modified Froude (Fr*) and capillary numbers (Ca). For Fr*<1, the oil–water interface topology is predominantly governed by the gravitational force exerted by an oil phase, whereas for Fr*>3.2 the interface topology is governed by the inertial force exerted by water. The interfacial tension force dominates for Ca<0.08 and 1>Fr*>1.6, Ca<0.04 and 1.6>Fr*>2.2.