A three-dimensional steady state arc model has been developed for simulating the behaviour of a twintorch plasma system operating in an atmospheric argon environment. The governing equations for plasma flow, electric and magnetic fields are solved in a Cartesian coordinate system with suitable domain size and appropriate boundary conditions. Radiation from the arc is accounted for using the concept of net emission coefficient. Results over the current range of 300A -900A suggest that the two

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... columns attached respectively to anode and cathode are coupled by a thin tissue-like conducting layer with a thickness in the range of 3-6mm, serving as a critical part of the current path. Lorentz force resulting from the arc's current interacting with its own magnetic field plays a decisive role in bending the two arc columns and shaping the coupling zone. Turbulence is introduced to account for the effect resulting from instability of the coupling zone as observed in experiment and its effectiveness is analysed in detail by using different length scale parameters. Suggestions to further improve the model are proposed. Confidential: not for distribution.