Efficient Kinetic/Continuum Simulations of Hypervelocity Gas Flows in Nonequilibrium Dissociation and Ionization for Earth Atmospheres

In this project, we propose an original method to simulate dissociated and ionized hypersonic air flows from continuum to rarefied regimes for a wide range of scales inherent in Air Force applications. We will introduce the most consistent physical model currently available in kinetic theory. The applicability range of fluid dynamical descriptions used for continuum flows can be extended to the transition regime by taking a finite sequence of moments of the Boltzmann equation together with a closure assumption. The resulting Boltzmann moment systems, solved by CFD methods, are computationally more efficient than statistical methods such as DSMC in the continuum and transition regimes. Therefore, we propose to develop a numerical scheme by blending the Boltzmann moment systems with Levermore closure and the DSMC technique, as opposed to traditional schemes based on the Navier-Stokes equations and DSMC. The coupling will be based on the concept of physics hybridization currently used to couple two vastly different representations of turbulent flows. In Phase I of this project, we will focus on the extension of the Boltzmann moment systems with Levermore closure to dissociating and ionizing hypersonic flows and the development of the computational strategy for the kinetic/continuum algorithm.