Description:
TECHNOLOGY AREA(S): Air Platform
OBJECTIVE: Develop a computational tool for analysis of laminar and turbulent hypersonic external flowfields in nonequilibrium to the required fidelity (high/low) for criteria driven by considerations of computational efficiency and reliability of prediction.
DESCRIPTION: High-speed ISR missions can be extremely challenging due to the complex flow behavior that includes interactions among various nonequilibrium physical phenomena for a broad range of length and time scales. This necessitates detailed representations of coupling between turbulent flow structures, and nonequilibrium energy exchange processes, such as the vibrational relaxation (vibration-translation exchanges), dissociation, electronic excitation and radiation for the high enthalpy flows in the Mach 6-12 flight regime. High fidelity numerical simulations include use of state-to-state kinetics for modeling nonequilibrium phenomena and direct numerical simulations (DNS) and large eddy simulations (LES) for flow turbulence. Detailed state kinetics based on master equations will include multiquantum rates obtained from one or more of the sources (or models) of quasi-classical trajectory (QCT), ab initio, or others such as the forced harmonic oscillator (FHO). These tools should be scalable for implementation on massively parallel computers and capable of both (a) direct numerical simulation and (b) reduced-order simulations. Lower fidelity modeling frameworks could include reduced-order models such as Landau-Teller, two-temperature vibration-dissociation coupling models, RANS turbulence models and other physics-based modeling approaches that can significantly reduce the computational complexity associated with turbulence and reactions but still maintain reliability of predictions. These tools should be versatile enough to allow for identification of dominant physical mechanisms in a broad range of flow scenarios and should enable new model development and validation. Criteria for model selection should be developed and implemented to allow for both high and low fidelities required for reliable predictive capability in an efficient manner. An integrated framework as a software deliverable containing these tools should be able to give reliable predictions of the aerothermodynamic flow field and quantities including drag, thermal loading, and gas surface interactions. An aero-optical analysis should be included but limited to illustration of the importance of fidelity of the aerothermodynamics modeling on signal propagation through the nonequilibrium laminar/turbulent external flowfields.
PHASE I: Develop, evaluate, and demonstrate predictive tools for three-dimensional (3D) laminar, hypersonic flows for both low fidelity and high fidelity state-to-state kinetics and criteria for model selection for both high/low fidelities.
PHASE II: Develop and validate predictive tools for 3D laminar and turbulent, hypersonic flows. High fidelity approaches for reacting turbulence will be based on DNS/LES and state-to-state kinetics. Develop criteria for model selection for both high- and low-fidelity approaches for reactive turbulence and demonstrate sensitivity of aerothermodynamics on signal propagation through simple aero-optic analysis. Document, deliver, and demonstrate predictive simulation tool to AFRL.
PHASE III: Commercialize the integrated tool for prediction of laminar/turbulent, hypersonic thermochemical nonequilibrium flows suitable for high-speed ISR missions. Government customers include Air Force, Army, Navy, and NASA. Commercial interests could include Lockheed, Northrop Grumman, and Boeing.
REFERENCES:
1. Josyula, E., Hypersonic Nonequilibrium Flows: Fundamentals and Recent Advances, AIAA Progress Series in Astronautics and Aeronautics, Vol. 247 (2015).
2. Josyula, E., Kustova, E., Vedula, P., and Burt, J., Influence of state-to-state transport coefficients on surface heat transfer in hypersonic flows, AIAA 2014-0864. Presented at the 52nd AIAA Aerospace Sciences Meeting (2014).
KEYWORDS: Hypersonics, Turbulence, State-to-state Kinetics, Nonequilibrium
