Analytical Theory of Aero-Optical and Atmospheric Effects in Supersonic and Hypersonic Flows
Anubhav Gupta (Author), Brian M. Argrow (Degree supervisor)
The traditional RF communication is not effective at high-speeds. Radio blackout is commonly associated with the interference from plasma created around high-speed aero-space and re-entry vehicles. Communication using lasers at optical frequencies has emerged as a promising counter to the problem. High-speed flows are characterized by drastic changes in the thermodynamic properties across the shock wave in a flow. The refractive index of a medium, such as air, governs the angular shift in the trajectory of an optical signal. For a fluid, the refractive index is a function of the thermodynamic states. The flow gradients in the shock layer of a three-dimensional geometry, such as cone, are responsible for refractive index gradient which result in continuous refraction of the optical signal. These angular shifts by the shock layer and the shock wave are further summed with the angular shift by atmospheric stratification. The variation of refractive index within shock layer, across shock wave and atmosphere, induces angular shift. An analysis of the horizontal shift in the signal's destination on reaching the surface, for air-to-ground communication, is crucial. The curvature of the Earth is an important factor to determine range of communication angle, horizontal shift, and ensure interception of signal on the surface. The analysis can be extended to the laser weapons for targeting. This thesis presents the development of an analytical framework to investigate the aero-optical and atmospheric effects on an optical signal when targeted from an aero-space vehicle for surface communication. The framework excludes the effects of - turbulence, boundary layer, and chemical reactions. The atmospheric refraction has been validated with the Cassini's model. The entire formulation has been verified computationally for wedge and cone in high-speed flows that capture effects from the flow gradients. Computational implementation of the framework is available as an open-source application software, referred AbRuAn after my family members name (Abhinav, Ruchi, Anil), under the MIT License
Thesis, Dissertation, English, 2020
ProQuest Dissertations & Theses, Ann Arbor, 2020