Aero-optical effects in non-equilibrium air
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© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. At hypersonic speeds, optical propagation and beam steering through shock waves and boundary layers are relevant to practical applications, such as imaging and flow sensing, as well as ground test and evaluation via application of schlieren and shadowgraph imaging techniques. In a flow environment which may induce real gas effects and chemistry, the refractive index depends on the air density, composition, and internal state. This paper describes an analysis of the effects of internal excitation on the molecular polarizability and refractive index of nitrogen and oxygen. In this analysis, the effects of non-equilibrium on the refractive index are examined. The results are discussed in the contest of accompanying experiments using a short-pulsed, low pressure discharge to recreate an environment with vibrational non-equilibrium. For experiments, a combination of optical emission spectroscopy and interferometry are applied in order to characterize the internal state of the gas simultaneously with the optical wavefront distortion and refractive index profile.
author list (cited authors)
Tropina, A., Wu, Y., Limbach, C., & Miles, R. B.