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Center for Nonlinear Studies |
Plasmas are ionized gas mixtures, either magnetized or not, that have many practical applications. For instance, the lunar return of the Orion Crew Exploration Vehicle involves significantly higher velocities (>10 km/s) than for the low orbit Earth reentry experienced by the Space Shuttle, enhancing the ionization degree of the plasma flow. The peak heating for the flight trajectory occurs in the continuum regime where kinetic theory can be used to obtain the macroscopic equations governing reentry flows and the expressions for the transport fluxes (diffusion of chemical species, momentum, and energy). Based on kinetic theory, we derive a general model for reactive plasmas, accounting for the electromagnetic field influence and an ionization mechanism. We deal with a possible thermal nonequilibrium of the translational energy of the electrons and heavy particles, such as atoms and ions, given their strong disparity of mass. We conduct a dimensional analysis of the Boltzmann equation and use, for the continuum regime, a multiscale Chapman-Enskog method to derive macroscopic conservation equations and expressions for the transport coefficients and chemical production rates. We have fully described the Kolesnikov effect, or crossed contributions to the mass and energy transport fluxes coupling the electrons and heavy particles. Our model satisfies the law of mass action and the first and second laws of thermodynamics. Finally, the development of numerical methods to solve conservation equations relies on the identification of their intrinsic mathematical structure. For instance, the system of conservation equations of mass, momentum, and energy is known to be nonconservative for thermal nonequilibrium ionized gases. We will show that kinetic theory, based on first principles, naturally allows for an adequate mathematical structure to be obtained, as opposed to the phenomenological approach.
Host: Rob Lowrie, lowrie@lanl.gov