Natural convection and thermal radiation in a circular cavity with a moving heat source and a tracking cold sink

This study investigates coupled natural convection and surface radiation in a circular air-filled cavity containing a moving heated block and a mobile cold sink governed by a thermal tracking strategy. The heated block undergoes oscillatory motion along the horizontal diameter, while the cooling sink occupies a movable boundary arc whose position is dynamically adjusted according to local thermal gradients to intercept the thermal plume generated by the moving source. Numerical simulations are performed using the finite element method, combining an Arbitrary Lagrangian–Eulerian (ALE) moving mesh formulation with automatic remeshing to accurately capture coupled motions. Thermal performance is evaluated through the convective, radiative, and total heat transfer rates, together with the mean and maximum cavity temperatures. A parametric study examines the effects of the thermal sensitivity threshold, sink mobility, wall emissivity, initial sink angular position, heated block size, and sink angular extent on heat transfer and thermal regulation. The results reveal a transition between two regimes: a mobile–fixed (M–F) regime with weak thermal coupling and a mobile–mobile (M–M) regime characterized by efficient plume tracking. The M–M configuration significantly enhances thermal performance, leading to higher heat extraction rates and lower mean and maximum temperatures. This improvement is associated with plume localization, intensified convective transport, and attenuation of periodic thermal oscillations, confirmed by spectral analysis. Increasing sink mobility improves tracking efficiency, whereas large thermal sensitivity thresholds degrade thermal regulation. These findings demonstrate that adaptive thermal tracking provides an effective strategy for heat management in systems involving moving heat sources.