Continuum-Kinetic Hybrid Framework for Chemically Reacting Flows

Predictive modeling of chemically reacting flows is essential for the design and optimization of future hypersonic vehicles. During atmospheric re-entry, complex flow structures form around the vehicle surface, exciting the gas molecules and causing chemical reactions. This work seeks to develop a multi-scale model for chemically reacting gas mixtures, which would have an immediate impact on applications involving entry, descent, and land (EDL) and thermal protection system (TPS) design. Simulation of these flow structures use hybrid approaches which model the gas differently according spatial region considered. Far from the vehicle surface, the gas flows are smooth, or equilibrium, and can be modeled using continuum fluid equations. Closer to the vehicle surface, the flows become more complex and are called non-equilibrium. This region is modeled using statistical techniques that track gas molecules individually. At the vehicle surface, it is also desirable to simulate the interactions of the gas molecules with the solid surface. These types of interactions are dependent on the microscopic characteristics of molecules and are simulated in molecular dynamics software. Understanding the nature of the gas flow in these three regions is key to characterizing the behavior of the gas around the vehicle. Previous research has successfully interfaced these three domains. However, these studies have not considered gases which could undergo chemical reactions. The goal of this work is to understand how the chemical reactions change the nature of the gas flow. To do this, a consistent treatment of chemistry models in each region will be investigated, as well as a rigorous coupling between the solutions in each region. From there, the effect of chemically reacting gas mixtures on the vehicle surface can be ascertained. This work will not deliver original software, but will provide a framework enabling these kinds of studies. There are many software packages available conducting simulations, which will be modified in this work. NASA in particular has been a pioneer in developing software for studying complex gas flows. Several NASA packages such as DPLR (Data Parallel Line Relaxation), LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm), and MAP (Multiphysics Algorithm with Particles) are being considered for use in this work. More »