Variation of the lift force components of a settling particle caused by structural evolution of flowing foam

Abstract

Wet foam fluid with a settling particle, as a special gas-liquid-solid three-phase flow, is increasingly found in related engineering fields. However, the detailed microscopic evolution of foam structure, which influences migration of the settling particle, has not been fully understood. In this study, the forces, exerted on the particle by foam film and bubble pressure in the flow direction, are defined as the lift force components Fnx and Fpx, respectively. The flow of the wet foam with a circular settling particle is studied by numerical method, and the distribution characteristics of the bubble-bubble and bubble-particle separations in the flowing foam are shown. More importantly, the influences of the microscopic structural evolution of foam film, such as the bubble-particle contact, the bubble-bubble and the bubble-particle separations, on the lift force components are in detail discussed. It is found that both the bubble-bubble and the bubble-particle separations can cause decreasing lift force and relaxing film stress, and the instantaneous bubble-particle contact can significantly change the lift force components. At the film scale, this study reveals the correlation between the particle movement and the microscopic structural evolution of foam fluid.