Probing the melting dynamics in a phase change Rayleigh–Bénard system under low gravity conditions

The present work aims to investigate dynamic characteristics of Rayleigh–Bénard convection during the solid–liquid phase change process under the influence of variable low-gravity conditions. Low-gravity conditions are crucial to gain physical insights into the complex convection dynamics relevant in terrestrial and space environments that feature diverse gravitational fields. The melting dynamics of a paraffin-based phase change material with Prandtl number Pr ≈ 71 in a square rigid walled enclosure is analyzed by subjecting it to a fixed temperature difference resulting in a Stefan number Ste ≈ 0.33. The enthalpy porosity method is employed to simulate the solid-liquid phase change process in Rayleigh number range 105<Ra <107 to take wide range of gravitational acceleration (0.0g, 0.1g, 0.2g, 0.4g, 0.6g, 0.8g, and g) into account. The simulation results allow detailed insights on the buoyancy-driven convective flow phenomena in a phase-change Rayleigh–Bénard system. Various characteristic flow regimes, the criteria for the onset of convective instabilities, and scaling analysis are presented under varied gravitational acceleration. The findings reveal that the critical Rayleigh number (Racr) for the onset of convection is found to vary between 1351.5 and 1810.5 under the gravity range investigated in contrast to the Racr ≈ 1707.7 for classical Rayleigh-Bénard system under the standard gravity. Furthermore, the scale analysis based on the numerical results shows that the relationship between effective Nusselt number (Nue) and effective Rayleigh number (Rae) follows a power law behavior Nue = 0.27Rae0.25 under each gravity condition, similar to the classical Rayleigh–Bénard system.