Numerical Methodologies for Non-Equilibrium Plasma Modelling

The development of reliable numerical tools for the simulation of non-equilibrium plasma devices is a fundamental requirement the technological progress. The main challenge in this context is to adequately represent multiple physical phenomena that take place over different temporal and spatial scales, while retaining reasonable computational performances. In the first part of the work, a fluid methodology in which electrons are modelled using the Boltzmann relation is developed as an alternative to Full Drift-Diffusion models. The proposed Boltzmann Drift-Diffusion methodology allows to limit the drift-diffusion approach to the ionic species, granting substantial savings in terms of computational performances. Both methodologies are applied to the 1D/2D simulation of a volumetric Dielectric Barrier Discharge reactor, operating with air at atmospheric pressure. A semi-implicit numerical technique for the integration of plasma kinetic processes is presented and numerically validated against a well established implicit methodology. The Boltzmann Drift-Diffusion and Full Drift-Diffusion approaches are compared. The obtained results are validated against experimental measurements of the deposited surface charge on to the dielectric layers covering the electrodes. In the second part of the work, a hybrid fluid/Particle-In-Cell approach is employed to model a miniaturized annular Hall thruster for space propulsion. The results yielded by two different treatments of the electron transport mechanism inside and outside the thruster channel are compared to macroscopic and microscopic physical information obtained through experimental measurements. These latter are then used to infer the anomalous transport collision frequency along the axis of the thruster. The obtained efficiency of the two chemical kinetic channels for the doubly charged ions production is discussed and correlated with the computed spatial distribution of the species.