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Center for Nonlinear Studies |
A vehicle entering the Earth’s atmosphere typically travels at many times the speed of sound, inducing a flow field characterized by strong shock waves, extreme temperatures, and thermal and chemical nonequilibrium. To accurately simulate hypersonic flows, models are required for chemical reactions and energy transfer between the translational and internal energy modes in the air. Presently, such models are outdated and of inadequate quality for advanced applications of interest to DOE, the Air Force, NASA, and other organizations. I will discuss an interdisciplinary study of fundamental chemical processes in hypersonic flows, focusing specifically on the gas-phase chemistry of nitrogen and oxygen. Early work involved the construction of accurate potential energy surfaces describing N2+N2, O2+O2, and N2+O2 interactions, based on new quantum-mechanical electronic structure datasets from the group of Prof. Donald G. Truhlar. Then, reactive collisions between diatomic species were simulated using the quasiclassical trajectory (QCT) method, which considers all rovibrational quantum states of the collision partners with minimal simplifications. Results from QCT and from a companion approach, the direct molecular simulation (DMS) method, shed new light on the mechanisms of diatomic dissociation and vibrational energy relaxation in high-temperature air. These data lay the foundation for macroscopic thermochemical models that are rigorously tied to first principles, and I will discuss current efforts to incorporate the project’s findings into hypersonic computational fluid dynamics simulations.
Host: Aric Hagberg