Numerical simulation of bubble motions in a coaxial annular electric field under microgravity

Gas-liquid separation under microgravity is a key scientific problem in space, which have wide application in future space systems. EHD has been proven an effective technique for enhancing two-phase separation by applying an electric field and induced electric forces to a dielectric fluid conveniently and adjustably. Although the electric effect on bubble dynamics of deformation and detachment are extensively studied recent years, the bubble motion behaviors which play an important role on phase separation under microgravity is seldom studied. In this paper, the motion behavior of a single air bubble surrounded by dielectric liquid CCl4 in a coaxial annular electrode electric field under microgravity is studied numerically to evaluate the potential phase separation applications under Microgravity. In the process of the numerical simulation, the Level Set (LS) method is employed to track the interface between the gas-liquid two phases, and a continuum surface force (CSF) model is used to calculate the surface tension force. Governing equations for the flow field and the electric field under microgravity are coupled numerically, which are solved by using an unstructured mesh system in the Cartesian coordinate system. Bubble motions including deformation and motion trajectory of the bubble, and flow patterns of the two-phase flow are payed close attention in this nonuniform electric field, where the underlying mechanism of EHD enhancement on phase separation is investigated. The simulation results indicate that the two-phase flow field and electric field interact and influence each other. The bubble would deform under the action of electric field force and move along the reduced direction of electric field, and the electric potential around the bubble would change compared with the initial state without the bubble in the nonuniform electric field under microgravity, which can greatly promote the gas-liquid two-phase separation in space. (C) 2019 Elsevier Masson SAS. All rights reserved.