  One of the challenges for development, qualification and optimisation of arc
welding processes lies in characterising the complex melt-pool behaviour which
exhibits highly non-linear responses to variations of process parameters. The
present work presents a simulation-based approach to describe the melt-pool
behaviour in root-pass gas metal arc welding (GMAW). Three-dimensional
numerical simulations have been performed using an enhanced physics-based
computational model to unravel the effect of groove shape on complex unsteady
heat and fluid flow in GMAW. The influence of surface deformations on
power-density distribution and the forces applied to the molten material was
taken into account. Utilising this model, the complex heat and fluid flow in
melt pools were visualised and described for different groove shapes.
Additionally, experiments were performed to validate the numerical predictions
and the robustness of the present computational model is demonstrated. The
model can be used to explore physical effects of governing fluid flow and
melt-pool stability during gas metal arc root welding.
