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A shock wave in a weakly ionized gas can be preceeded by a charge separation region if the Debye length is larger than the shock width. It has been proposed that electrostatic contributions to pressure in the charge separation region can increase the sound speed ahead of the shock well above the sound speed in a neutral gas at the same temperature and therefore increase the shock propagation speed. This proposal is investigated numerically and theoretically. It is concluded that although the ion gas becomes strongly non-ideal in the charge separation region, there is no appreciable effect on the neutral shock.
An analysis and assessment of three mechanisms describing plasma/ shock wave interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of ion-acoustic wave damping, post-shock energy addition and thermal inhomogeneities were examined by numerically solving the Euler equations with appropriate source terms adapted for each mechanism. Ion-acoustic wave damping was examined by modeling the partially ionized plasma as two fluids in one spatial dimension using the Riemann problem as a basis. Post-shock energy addition in the form of nonequilibrium vibrational energy relaxation was also examined in one spatial dimension using the Riemann problem as a basis. The influence of thermal inhomogeneities on shock wave propagation was examined in two spatial dimensions for both a Riemann shock and a shock generated by a spark discharge. Shocks were propagated through realistic thermal profiles with the resulting shock structure examined through the numerical application of various optical diagnostic techniques. Results from shock simulations indicate that ion-acoustic wave damping has an insignificant effect on the neutral flow at fractional ionization levels typical of glow discharges. Post-shock vibrational energy relaxation is also unable to effect the shock structure on the time scales of interest. An analysis of the effects of thermal inhomogeneities reveals that many of the observed plasma/shock anomalies can be explained based solely on this mechanism.
The multi-component continuous approach for the investigation of the gasdynamics of a plasma is presented. More information about the flow properties of a plasma can be obtained than from the classical magnetohydrodynamic approach. Also, the resulting equations appear to be more easily solved than the Blotzmann equation of classical kinetic theory. The basic macroscopic conservation equations for a non-reacting multi-component plasma are presented. The fluid properties of each component are referred to the mean velocity of that component. Therefore, no limitations are placed on the magnitude of the diffusion velocities. The effects of electric and magnetic fields are included. The equations for a two-component mixture are used to study the structure of a shock wave in a fully-ionized hydrogen gas. It is assumed that the momentum exchange and energy exchange between the ions and electrons are important because of the strong Coulomb forces present. (Author).
The structure of a shock wave in a partially ionized gas, which is in thermal on-equilibrium ahead of the shock wave, is investigated. A method is developed to solve this problem by separating it into two parts. First the structure of the shock wave associated with the mixture of ions and atoms, which are assumed to behave alike through the shock transition, is taken to be of the Mott-Smith form. Then the behavior of electrons as they pass through this ion-atom shock is analyzed. Using this method, calculations are made for the shock wave structure in partially ionized argon for Mach numbers equal to 8, 10 and 12, and for the values of the lectron-ion temperature ratio ahe d of the shock wave equal to 3, 5 and 8. (Author).
Results are given for equilibrium properties behind incident and reflected normal shock waves in CO2-N2-He mixtures wherein the gas may be vibrationally excited but not chemically reacting. A rapid numerical iterative analysis is described, and the results are given in simple graphical form for convenient use in shock tube and shock tunnel experiments. The results are anticipated to be of particular use in determining reservoir conditions for shock tunnel experiments dealing with vibrational population inversions in rapidly expanding mixtures. (Author).