This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Decontamination of sensitive surfaces and sterilization of living tissue using traditional high temperature or chemical surface treatment methods may destroy the required functionality of the surface. For these surfaces, small-scale cold plasma jets produced in atmospheric air can provide an alternative by using regions of highly reactive chemistry that are near room temperature. Plasmas are inherently multiphysics phenomena, and feature a tightly coupled system of electromagnetics, fluid flow, physical kinetics, chemical reactions and heat transfer, as such any attempt to develop the technology using traditional testing and evaluation methods is inherently unstable.

Computational simulation can be used to help design plasma devices and operating conditions that optimize the effectiveness of cold plasma jets, however due to the strong coupling that occurs between the electric field, fluid flow, physical kinetics, chemical reactions, and heat transfer, the simulation of plasma jets is a challenging multiphysics problem. In this work, air at atmospheric pressure flows through a hollow anode and cathode. Prior to exiting the device, the air is subjected to a strong electric field that results in the development of a plasma jet at the nozzle exit. The small diameter of the plasma and the turbulent heat transfer in the flow lead to the development of a plasma jet that is sustained at a low temperature, while the reactive species that are developed in the plasma continue to exist some distance away from the nozzle.

In the current work, a fully coupled analysis of an air plasma jet has been performed using COMSOL Multiphysics®. The non-equilibrium, non-Maxwellian plasma is modelled using a fluid approximation that solves for the transport of the electron density and the mean electron energy, and the two-term Boltzmann equation is used to calculate the transport coefficients and electron impact reaction rate coefficients. The plasma chemistry includes 19 species and 183 reactions, and transport equations are solved for each species. To solve for the momentum transport of the bulk fluid, the k-? turbulence model is used. The plasma, species transport, and fluid flow equations are coupled to together and to a heat transfer equation for conduction and convection, including the effect of turbulent flow. The simulation results have been used to predict the temperature distribution and the concentrations of reactive species within the jet.