Stability of flowing PbLi alloy between coaxial cylinders under magnetic field

Abstract

In this research, numerical simulations were performed to investigate the stability of a flowing PbLi alloy (Pr = 0.032) within two coaxial vertical cylinders, while subjected to an axial magnetic field. The primary objective of this study was to analyze how the presence of the axial magnetic field affected both vortex breakdown and swirling flow phenomena. To achieve this, the governing equations, which included the Navier-Stokes equations and potential equations, were solved using the finite-volume method. The numerical simulations presented results for three aspect ratios (A= 1.5, 2.0, and 2.5) and three annuli (R = 0.9, 0.8, and 0.7). In the hydrodynamic scenario, vortex breakdown was observed close to the inner cylinder as a result of the intensified pumping effect caused by the Ekman boundary layer. The findings demonstrated that the onset of oscillatory instability was initiated by increasing the Reynolds number to a critical value. However, when a magnetic field is intensified, the vortex breakdown vanishes, and its limits will shrink. Stability diagrams were created to depict the boundaries within which a vortex breakdown bubble emerges, allowing for a visual picture of its occurrence