Ionizing argon boundary layers. Part 1. Quasi-steady flat-plate laminar boundary-layer flows

Details are given of an implicit six-point finite-difference scheme for solving two-temperature, laminar, boundary-layer flows not in chemical equilibrium in ionizing argon. The analysis extends previous work by considering the radiation-energy loss and the chemical reactions due to atom-atom and electron-atom collisions in the ionizing boundary-layer and free-stream flow. Also included are variations in transport properties based on known elastic-scattering cross-sections, effects of chemical reactions, radiation-energy loss and the electric-sheath wall boundary conditions. The results are compared with dual-wavelength interferometric boundary-layer data obtained by using a Mach-Zehnder interferometer 23 cm in diameter with the UTIAS 10 × 18 cm Hypervelocity Shock Tube for shocks of initial Mach numbers M s ∼ 13 and 16 moving into argon at a pressure p0 ∼ 5 torr and temperature T0 ∼ 297 °K. Considering the difficulties involved in solving such complex plasma flows, satisfactory agreement was obtained between analytic and experimental total-density profiles and electron-number-density profiles for the case M s ∼ 16 and good agreement for M s ∼ 13.