Role of Hypervelocity Mach Numbers on Optical Distortion
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Date
2023-11-22
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Abstract
To characterize optical distortion in a hypervelocity ground test facility, a study comparing effects at three hypersonic Mach numbers simulated at true flight conditions was conducted. A highly modifiable wedge model and a beam distortion imaging technique were designed and implemented in Texas A&M University’s Hypervelocity Expansion Tunnel. Additionally, optical diagnostics, such as high-speed schlieren, optical emission spectroscopy, and focused laser differential interferometry were conducted. A laminar 11-species gas computational fluid dynamics model was run over the geometry to determine the level of species excitation resulting from the stagnation region. A comparison of optical distortion, index of refraction spectra, and index of refraction gradient spectra at Mach 9, 12, and 15 was conducted. The results confirmed the laminar boundary layer and shock layer 15.5 cm aft of the nose for Mach 12 and 15, but the Mach 9 flow was transitional. Additionally, maximum beam distortion occurred at Mach 9 due to a higher density flow-field. These investigations led to recommendations for refining the beam distortion imaging in HXT and geometry changes to the model to study turbulence.
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Optical Distortion, Hypervelocity, interferometry, Mach 9, Mach 12, Mach 15