Rate-dependent energetic processes in hypersonic flows

In celebration of the first 60 years of the Air Force Office of Scientific Research, several studies of hypersonic flows dominated by rate-dependent energetic processes are revisited. The work presented shows the evolution and advancement of computational capabilities in this area, and illustrates some key lessons learned over the previous decade or so. Early work with Leyva and Hornung in the California Institute of Technology T5 Free-Piston Shock Tunnel had the goal of validating thermochemical models for high-enthalpy flows. Several of these flows are re-analyzed with more advanced numerical methods, resulting in improved comparisons with the experimental measurements. This work was followed by a series of experiments in the Calspan-University at Buffalo Research Center (now CUBRC Inc.) facilities at lower enthalpy conditions. Initial comparisons were poor, but with a better understanding of the facility behavior and the inclusion of key finite-rate processes, excellent agreement was obtained for nitrogen flows. An interesting study related to plasmadynamics and finite-rate processes in a different type of flow is discussed. Finally, it is shown that recent advances in numerical methods that are beginning to enable the direct numerical simulation of key rate-dependent energetic processes in hypersonic flows.