Influences of Sign of Surface Tension Coefficient on Turbulent Weld Pool Convection in a Gas Tungsten Arc Welding (GTAW) Process: A Comparative Study

The effects of positive and negative surface tension coefficients $(∂σsur∕∂T)$ on both laminar and turbulent weld pool convection are numerically studied for a typical gas tungsten arc welding (GTAW) process. Three-dimensional turbulent weld pool convection in a pool is simulated using a suitably modified high Reynolds number $k‐ε$ model in order to account for the morphology of an evolving solid-liquid interface. Key effects of the sign of surface tension coefficient $(∂σsur∕∂T)$ on the turbulent transport in a GTAW process are highlighted by comparing the turbulent simulation results with the corresponding ones from a laminar model, keeping all other process parameters unaltered. A scaling analysis is also performed in order to obtain order-of-magnitude estimates of weld pool penetration for both positive and negative surface tension coefficients. The scaling analysis predictions are in good agreement with the numerical results, in an order-of-magnitude sense.