This study performed three-dimensional transient numerical simulations using the volume of fluid method in a gas metal arc V-groove welding process with and without root gap for flat, overhead, and vertical welding positions. The elliptically symmetric arc models for arc heat flux, electromagnetic force and arc pressure were used to describe the more accurate molten pool behaviors. The numerical models not only formed a stable weld bead but also simulated the dynamic molten pool behaviors such as overflow which was not described before. This study analyzed these molten pool flow patterns for various welding positions and validated the numerical models used by comparing the simulation results with experimental ones. (C) 2013 Elsevier B.V. All rights reserved.