Multi-scale two-domain numerical modeling of stationary positive DC corona discharge/drift-region coupling

Abstract

Abstract Corona discharge modelling mostly relies on two, mostly distinct, approaches: high-fidelity, numerically challenging, unsteady simulations having high-computational cost or low-fidelity simulations based on empirical assumptions such as constant electric field at the emitter electrode. For the purpose of steady discharge current predictions, high-fidelity models are very costly to use whilst empirical models have limited range of validity owing the subtle use of tuned parameters. We propose an intermediate approach: an asymptotic multi-scale/two-domain numerical modeling based upon generalizing previous asymptotic axi-symmetrical analysis [1] , [2] . We show how the initial elliptic (electric potential), hyperbolic (charge transport), non-local (photo-ionization) problem can be formulated into two local problems coupled by matching conditions. The approach relies on a multipole expansion of the radiative photo-ionization source term (in two dimensions for cylindrical emitters). The analytical asymptotic matching conditions derived in [2] result in flux continuity conditions at the boundary of the two domains. These coupling conditions are enforced by Lagrange multipliers, within a variational formulation, leading to a hierarchy of non-linear coupled problems. The proposed approach is both monolithic and two-domains: two asymptotic regions, an inner-one associated with corona discharge, and an outer-one, the ion drift region. Numerical convergence and validations of the finite element implementation is provided. A comparison with various experimental results convincingly demonstrate the applicability of the method, which avoids tuning parameters dedicated to each specific configuration, but, on the contrary, exclusively relies on known and measurable physical quantities (e.g, ion mobilities, photo-ionization coefficient, ionization electric field, Townsend discharge coefficient, etc...).