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Published online by Cambridge University Press: 17 July 2025
Direct numerical simulations have been conducted to explore the coupling effect of the thermoelectric effect and vertical convection (VC) in a square cavity composed of liquid lithium and stainless steel under different Hartmann numbers at $Ra=10^5$. By leveraging thermoelectric phenomena, an innovative approach is proposed to actively modulate heat transfer efficiency. The core concept lies in modulating the intensity of large-scale circulation (LSC) in VC systems through the torque generated by the interaction between thermoelectric currents and magnetic fields via Lorentz forces. The findings reveal that when the torque aligns with the direction of LSC induced by pure buoyancy, both momentum and heat transfer are enhanced. However, due to the magnetic damping itself, this enhancement is not sustained indefinitely, resulting in a trend of initial increase followed by decline in both momentum and heat transfer efficiency. Conversely, when the magnetic field direction is reversed, causing the Lorentz force torque to oppose the buoyancy-driven circulation, both momentum and heat transfer efficiency diminish until the flow reverses. By varying the magnetic field intensity, three distinct flow regimes are identified: the buoyancy-dominated regime, the thermoelectric-dominated regime and the magnetic-damping-dominated regime. The transition between the buoyancy-dominated regime and thermoelectric-dominated regime – specifically, the onset of flow reversal – is analysed through a boundary-layer–bulk–boundary-layer coupling model. This model enables precise prediction of the critical
$Ha$ based on the torque balance between buoyancy forces and thermoelectrically induced Lorentz forces, and demonstrates close agreement with numerical simulations.