| dc.description.abstract | Improved modeling of hypersonic turbulent shear layers is of national interest. The Reynolds
numbers experienced preclude widespread use of high fidelity simulations, and the complexity of the flow is not captured by simpler techniques derived for low speed applications. The extreme temperatures characteristic of hypersonic environments and the thermochemical effects they engender remain a challenge for the current theory, but their accurate prediction is imperative for vehicle designers. This body of work covers the theory, modeling, and experimentation of a hypersonic turbulent boundary layers with and without thermal nonequilibrium. An existing low fidelity, low cost algebraic energy flux model was re-derived to great detail, allowing it to be more easily implemented, assessed, and extended to cases with thermal nonequilibrium. It was integrated into a simple numerical boundary layer solver, which was written to guide subsequent experiments. Experimental data for the validation of turbulence models was provided from a 2.75° half-angle wedge tested at M = 5:7 and Re = 6 x 10⁶∕m in the Actively Controlled Expansion tunnel. Specifically designed trips fomented turbulence over the test article and a 47W direct current glow discharge instilled vibrational nonequilibrium. Both on- and off-body visualization, temperature, frequency, and velocity data sets collected with a variety of techniques are included herein. Redundancy in the techniques ensured the veracity of the data, and allowed global trends to be identified. Of particular interest to turbulence model validation were mean and fluctuating velocity and temperature data collected using NO planar laser-induced fluorescence. This technique was also used to study the vibrational relaxation of NOᵛ⁼¹ in the boundary layer along the test article. These data, the first known survey in a hypersonic turbulent boundary layer, suggested the vibrational relaxation and flow timescales were comparable, allowing the possibility the two separate mechanisms could interact. To summarize, an exhaustive database of boundary layer data was generated which could serve to validate existing and future turbulence models. These would allow better prediction of vehicle heating in hypersonic environments. | |
