The Example of Using MHD Theory and CFD Software for Simulating the Behavior of an Electric Arc

This paper presents the possibilities of using MHD (Magnetohydrodynamics) theory for analyzing the behavior of an electric arc, with the use of CFD (Computational Fluid Dynamics) software tools. These software packages are based on the finite element theory, with the assumption of local thermodynamic equilibrium (LTE). This approach treats the electric arc as a conductive fluid, including all its electromagnetic properties. The simulation was conducted using Ansys Fluent software, through the built-in MHD module, as well as user-defined functions (UDFs). As an example, an initialized plasma channel of an electric arc was considered based on a model found in the literature, which was simplified to save computational resources and simulation time. The model includes the anode, cathode, and the so-called "splitter," which serves to separate the arc, cool it down, and increase its resistance. The movement of the arc is demonstrated through natural dynamics caused by temperature increases, as well as forced movement due to the Lorentz force from an external magnetic field. Due to these factors, the electric arc moves upward through the geometry design, increasing its length, after which separation and cooling occur, significantly reducing the conductivity of the plasma channel as its length increases. The surrounding medium is air. The paper covers all necessary aspects of modeling the electric arc, as well as the selection of appropriate physical models that describe the properties of air during the arc’s duration. This simulation demonstrates the potential use of the aforementioned theory for analyzing various geometries of switching equipment in alternating and direct current systems, which could serve as a significant complement to practical experiments.