Electric welding arc modeling with the solver OpenFOAM - A comparison of different electromagnetic models

Paper i proceeding, 2011

This study focuses on the modeling of a plasma arc heat source in the context of electric arc welding. The model was implemented in the open source CFD software OpenFOAM-1.6.x, coupling thermal fluid mechanics in three dimensions with electro magnetics. Four different approaches were considered for modeling the electromagnetic fields: i) the three-dimensional approach, ii) the two-dimensional axi-symmetric approach, iii) the electric potential formulation, and iv) the magnetic field formulation as described by Ramírez et al. [1]. The underlying assumptions and the differences between these models are described in detail. Models i) to iii) reduce to the same quasi one-dimensional limit for an axi-symmetric configuration with negligible radial current density, contrary to model iv). Models ii) to iv) do not represent the same physics when the radial current density is significant, such as or an electrode with a conical tip. Models i) to iii) were retained for the numerical simulations. The corresponding results were validated against the analytic solution of an infinite electric rod. Perfect agreement was obtained for all the models tested. The results from the coupled solver (thermal fluid mechanics coupled with electromagnetics) were compared with experimental measurements for Gas Tungsten Arc Welding (GTAW). The shielding gas was argon, the arc was short (2mm), the electrode tip was conical, and the configuration was axi-symmetric. The boundary conditions were specified at the anode and cathode surfaces. Models i) and ii) lead to the same results, but not the model iii). Model iii) neglects the radial current density component, resulting in a poor estimation of the magnetic field, and in turn of the arc fluid velocity. The limitations of the coupled solver were investigated changing the gas composition, and using different boundary conditions. The boundary conditions, difficult to measure and to estimate a priori, significantly affect the simulation results.