Unstable thermocapillary convection in metal liquid bridge is a typical phenomenon during the laser metal-wire additivemanufacturing process in microgravity environment. The evolution and dynamic mechanism of the liquid bridge willinfluence the manufacturing process and quality for the forthcoming on-orbit space metal additive manufacturing.Therefore, it is very important to investigate the evolution and instability of thermocapillary convection in liquid bridgesin microgravity. In present investigation, a numerical model is developed to reveal the characteristics of thermocapillaryconvection. The effects of aspect ratio and gravity on the critical Reynolds number for convection instability ofthermocapillary convection in metal (Ti6Al4V) liquid bridge are investigated numerically. The results indicate that thecritical Reynolds number for convection instability decreases with the increase of aspect ratio number at first, and thenincreases both in the gravity or microgravity environment. The numerical results also reveal that the critical Reynoldsnumber for convection instability under gravity environment with natural convection in metal liquid bridge is larger thanmicrogravity environment. The research shows that the influence of microgravity leads to a distinctly different behaviourof thermocapillary convection in metal liquid bridge compared to the gravity environment. A more comprehensive studywill be conducted to cover the parameter space more systematically to identify the factors which significantly influencethe stability of the thermocapillary convection in metal liquid bridge under microgravity environment, which is importantfor the on-orbit space metal additive manufacturing.
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