Supersonic, nonequilibrium corner expansion flow of ionized argon

The nonequilibrium corner-expansion flow field of partially ionized argon was solved numerically using the method of characteristics. The solution assumed a steady, two-dimensional, and inviscid field. The main feature of the present solution, as compared with previous numerical solutions for the corner-expansion flows, is in the relaxation of the requirement that thermal equilibrium be maintained throughout the expansion. As a result, the electron temperature was found to be higher than that of the heavy particles. This is expected, since most of the energy released during the recombination process is absorbed by the free electrons. The specific solution reported here, solved the expansion field for two different corners (-5° and -15° expansion angle), when both had the same pre-corner flow conditions. Fair agreement was found between the present numerical solution and the experimental results regarding the density and degree of ionization changes along streamlines. Consequently, the present technique can be used with confidence for the flow of various plasmas.