Computational 3D Modeling and Simulation of DC Atmospheric Pressure Glow Discharge in Helium

Atmospheric pressure glow discharges (APGDs) are used in diverse established and emerging applications such as lighting, spectroscopy and diagnostics, materials processing, chemical synthesis, environmental remediation, and medicine. APGDs have been widely studied through computational models, yet not nearly to the extent of their low-pressure counterparts. Particularly, three-dimensional (3D) models of APGDs have been scarcely reported in the research literature. However, the description of physical phenomena such as pattern formation and self-organization, particularly observed in APGDs with liquid electrodes, require 3D models. Moreover, the majority of APGD models neglect advective gas transport, which limits the suitability of those models for the description of discharges with significant gas heating, as found at relatively high electric current operation. A computational 3D time-dependent model of APGD in helium is presented. The model describes the plasma as a quasi-neutral fluid in thermodynamic and chemical nonequilibrium and is composed by the equations of conservation of total mass, species mass, mass-averaged momentum, energy of heavy-species (i.e., He, He * , He + , He 2 * , He 2 + ), energy of electrons, and charge (Poisson equation). Reaction rates are determined through collision cross-sections from BOLSIG+ as well as by rates reported in the literature. The model is solved by the in-house developed solver TPORT 1 , which handles the model equations in a fully-coupled monolithic approach as a set of transport equations and discretizes them using a Variational Multiscale Finite Element Method Formulation. The model is applied to the simulation of a pinto-plate self-sustained atmospheric pressure glow discharge in the range of tens of milliamps. The computational model is complemented with an external circuit model to specify the electric potential boundary condition such to impose a user-specified value of total current. Simulation results are shown to be in agreement with experimental results reported by Arkhipenko and collaborators 2 .