Anisotropic Lorentz force effects on the Marangoni convection in liquid metal systems for fusion applications.

Abstract

This study investigates Marangoni convection in a liquid metal-filled cubic cavity, relevant to fusion reactor plasma-facing components, using three-dimensional direct numerical simulations with a self-developed magnetohydrodynamic (MHD) code. The effects of magnetic field strength (Hartmann number, Ha = 0-200) and orientation (x, y, z directions) are analyzed at a fixed Reynolds number (Re = 100,000). Strong magnetic fields suppress convection, with the x and y directions exhibiting greater suppression than the z direction. Lorentz forces in the x-direction minimally affect surface flow while suppressing core motion, whereas in the y-direction, they significantly reduce surface velocity, leading to an M-shaped velocity profile. In contrast, a z-directional field induces a non-monotonic heat transfer efficiency, enhancing the Nusselt number at low strengths (Ha < 30) by augmenting Hartmann layer flow and suppressing it at higher strengths (Ha = 200) due to flow inhibition. These findings reveal distinct flow structure variations driven by anisotropic Lorentz force effects, providing critical insights for optimizing liquid metal applications in magnetic confinement fusion systems.