Aerospace Systems Directorate, RQ/Aerospace Structures, Aerodynamics, and Flight Controls
||Wright-Patterson AFB, OH 454337542
The flight envelope of the next generation of hypervelocity aerospace vehicles powered by air breathing propulsive devices includes extended dwell time at relatively high altitudes. The design space of such vehicles can only be analyzed by acquiring a detailed understanding of a broad spectrum of spatio-temporal time scales for a wide array of internal energy modes of rotation, vibration, dissociation, and radiation for both laminar and turbulent flowfields. Hypervelocity flows are distinctive in the high-temperature regime because of the finite rates at which the energy modes in the atmospheric air get excited and eventually dissociate and ionize. Since these processes take place at finite rates, their accurate computation impacts surface heat transfer prediction accuracy and consequently the design of the thermal protection system. Currently, numerical methodologies to address the continuum and rarefied regimes are often distinct. However, there has been a resurgence in the calculation of ab initio rates from several groups, notably for the nitrogen and oxygen gases. Thus, it is essential to develop highly accurate physical models and to couple them to advanced, robust numerical methods which can exploit massively parallel modern computational systems. Broad research opportunities exist to (1) develop and implement highly accurate algorithms for a hierarchy of theoretical models of increasing fidelity for various levels of fidelity in nonequilibrium descriptions; (2) utilize computational tools to assess sensitivity of nonequilibrium models; (3) develop, implement, and validate models using state-to-state kinetics for developing reduced order models; (4) develop, implement, and validate gas surface interactions to predict realistic heat transfer in high temperature flow conditions; and (5) explore the hypersonic design space to discover new vehicle concepts.
Josyula E, Bailey WF, Suchyta CJ: "Dissociation Modeling in Hypersonic Flows Using State-to-State Kinetics." Journal of Thermophysics and Heat Transfer 25(1): Jan-Mar 2011
Burt JM, Josyula E: "Assessment of Vibrational Nonequilibrium for State Resolved Simulation of a Hypersonic Flow." AIAA 2016-0737, Presented at SciTech 2016 held 4-8 Jan 2016, San Diego, California, USA.
State-to-state kinetics; Ab-initio rates; Master equation; Rotational energy; Vibrational energy; Dissociation; Gas surface interactions; Reduced order models; Computational algorithms; Fluid dynamics modeling; Hypersonic flight;