Quasi-One-Dimensional, Nonequilibrium Gas Dynamics of Partially Ionized Two-Temperature Argon

A set of equations governing the quasi-one-dimensional flow of a nonequilibrium argon plasma is formulated. The kinetic model includes ionization by atom-atom and electron-atom impacts, together with the three-body recombination counterparts of these processes. The electron gas temperature—a key variable in controlling ionization reaction rates in a noble gas—is not necessarily equal to that of the heavy particles and must in general be found by simultaneous solution of a differential electron energy equation together with the usual conservation equations. Numerical solutions are obtained for the special case of the relaxation zone behind strong normal shocks which give good agreement with shock tube measured ionization times. For these normal-shock calculations, a local steady-state approximation to the electron energy equation is found to be useful in view of an insensitivity, demonstrated by the numerical results, to arbitrarily selected initial values of post-translational shock electron temperature.