NUMERICAL METHOD AND RESULTS OF COMBINED SOLUTION OF KINETIC AND RADIATION TRANSPORT EQUATIONS IN NONEQUILIBRIUM PLASMA

E.V. Groshev, V.A. Zhmailo
VANT. Ser.: Mat. Mod. Fiz. Proc 1997. Вып.1. С. 51.

      Some engineering and science applications use plasma radiation. Furthermore, it is frequently used for the diagnostics of plasma parameters.
      If the emitting plasma is in nonequilibrium, the calculation of its properties and radiation characteristics requires combined computations of kinetics, energy and radiation transport equations. -
      This work presents one of the approaches to the solution of such problem. Its specific feature is the kinetics model considered: it is oriented to the description of plasma in a wide range of temperature and density variations. The gas is assumed to be composed of one mixture of particles (atoms, molecules and ions). The kinetics includes the following processes: electron shock ionization, molecules dissociation by the electron shock, dissociation recombination, photo-ionization, associative ionization, molecules dissociation by heavy particles, recharging, photorecombination and recombination in triple collisions. Energy equations are written for ions and electrons; these equations account for the energy transfer between electrons and heavy particles resulting from elastic and nonelastic collisions as well as from the interaction with radiation.
      The absorption coefficients are calculated from Kramers-Unsold approximation, the radiation transport in the lines is ignored. The gas is assumed to be fixed, the problem is one-dimensional and spherically symmetric.
      The process is described by the system of photon transport, kinetics and energy equations for ions and electrons. The system is approximated with the first order implicit scheme in time. The transport equation is approximated with actually monotonic ST_n scheme in space [1]. The system of difference equations at the timestep is solved with the method of “simple” iterations involving the convergence acceleration algorithm [2]. The system of kinetics and energy equations is solved with Newton method.
      The illustration is given based on the problem describing the radiation from rarefied air heated by the external source. The description is given for the energy redistribution over space due to the radiant transport and gas composition changes.
      1. Groshev E.V., Pastushenko A.M., Yudinisev V.F. One three-point difference scheme with the weight factor for the transport equation // Voprosy Atomnoy Nauki i Tekhniki. Ser. Metodiki i Programmy Chislennogq Resheniya Zadach Matematicheskoy Fiziki. 1985. N 2. P. 87-96.
      2. Groshev E.V. One iteration convergence acceleration method for numerical calculation of 1-D nonstationary radiation transport in multigroup kinetic approximation // Ibid. 1982. N 1. P. 67-72.