Comparison of turbulence models for a free-burning high-intensity argon arc

Abstract

Free-burning arcs where the work piece acts as an anode are frequently used for a number of industrial applications. Our investigation was concerned with developing a capability to model free-burning high-intensity argon arcs and enhancing the accuracy of numerical results according to a comparative study of turbulence models. For the arc modeling involved complicated interactions between the flow and electromagnetic fields, we modified the Navier-Stokes equations to take into account the radiation transport, the electrical power input and the electromagnetic driving forces with the relevant Maxwell equations. For the turbulence modeling, which is critical to the arc edges due to a steep temperature gradient between the arc column and the surrounding gas, zero- and two-equation eddy-viscosity models were used. The major arc parameters of temperature, axial velocity, electric potential difference and pressure-rise from ambient atmospheric pressure were summarized under laminar and turbulent conditions. It was found that the standard k-ɛ model modified to take into account the effect of a steep temperature gradient at the edge of free-burning arcs could predict reasonable temperature profiles better than the cases with the assumption of laminar flow and Prandtl’s mixing length model used for switching arcs.