Some physical aspects of the nonequilibrium, supersonic, corner expansion flow of ionized gases

The flow fields of supersonic, nonequilibrium corner expansion flows of ionized gases have been solved numerically, for three different gases, using the method of characteristics. Special attention has been given to the effect that the gas mass and its ionization potential have upon the solution obtained. It was found that the ratio between the atomic mass of the element considered and its ionization potential m_a/θ₁, plays an important role in establishing thermal equilibrium. Gases having a small value of m _a/θ₁, will approach thermal equilibrium at a faster rate than those having a larger value of m_a/θ₁. On the other hand, the approach to chemical equilibrium is controlled by the recombination rate which is strongly temperature dependent. Therefore, fast reduction in temperature, in the expansion field, promotes a rapid approach to chemical equilibrium. The effect of the electron-atom collision cross section σ_ea, on the numerical results obtained, is also studied. It is shown that accurate knowledge of σ_ea is required to evaluate the plasma electronic properties (T_e and α), but even a rough estimate of σ_ea is sufficient for the evaluation of the gross properties of the plasma (p, ρ, and T).