COMPUTATIONAL FLUID-DYNAMICS MODELING OF MULTICOMPONENT THERMAL PLASMAS

A comprehensive computational model has been developed for flowing thermal plasmas in the absence of electromagnetic fields, with particular emphasis on plasma jets. The plasma is represented as a multicomponent chemically reacting ideal gas with temperature-dependent thermodynamic and transport properties. The plasma flow is governed by the transient compressible Navier-Stokes equations in two or three space dimensions. Turbulence is represented by subgrid-scale and k-epsilon models. Species diffusion is calculated by an effective binary diffusion approximation, generalized to allow for ambipolar diffusion of charged species. Ionization, dissociation, recombination, and other chemical reactions are computed by general kinetic and equilibrium chemistry algorithms. Radiation heat loss is currently modeled as a temperature-dependent energy sink. Finite-difference approximations to the governing equations are solved on a rectangular spatial mesh using explicit temporal differencing. Computational inefficiency at low Mach number is avoided by reducing the effective sound speed. The overall computational model is embodied in a new computer code called LAVA. Computational results and comparisons with experimental data are presented for LAVA simulations of a steady-state axisymmetric argon plasma jet flowing into cold argon.