Numerical study of the interaction between a bubble rising in a column of conducting liquid and a permanent magnet

N. Tran¹ - T. Boeck² - U. Lüdtke¹ - Z. Lyu² - C. Karcher²

¹ Institut für Elektrische Energie- und Steuerungstechnik, Technische Universität Ilmenau, 98693 Ilmenau, Germany
² Institut für Thermo- und Fluiddynamik, Technische Universität Ilmenau, 98693 Ilmenau, Germany e-Mail: ninh.tran-thi-hang@tu-ilmenau.de

Abstract
Electromagnetic induction in a conducting liquid that moves in an external magnetic field can be used for contactless flow measurement. In Lorentz Force Velocimetry (LFV), the induced force on the magnet is determined to obtain velocity information. This measurement principle may also be applied to conducting flows with gas bubbles encountered in metallurgical processes. This provides the motivation for our work, in which we study a single bubble rising in a liquid metal column as a model problem for LFV in two-phase flows. By using a small permanent magnet, one can not only detect the presence of a bubble but also obtain information on its position and velocity. Our numerical investigation aims at reproducing experiments with Argon bubbles in GaInSn alloy and at studying the electromagnetic induction in the flow in more detail. For three-dimensional and phase-resolving simulations we use the Volume of Fluid method provided by ANSYS FLUENT. The induction equation in the quasistatic limit is an elliptic problem for the electric potential. It is implemented in FLUENT with a user-defined scalar. The electric conductivity varies between the phases, and the magnetic field is given by an analytical expression for a uniformly magnetized cube. The comparison with the experiments also helps to validate the numerical simulations. Tables 1, Figs 9, Refs 22.