Doctor of Philosophy, The Ohio State University, 2018, Aero/Astro Engineering

Robust and expedient prediction of the aerothermodynamic loads is critical to the development of modern reusable high-speed platforms. However, the presence of complex flow physics, including strong inviscid-viscous interactions, impinging shocks, and intense three-dimensionality, poses a significant challenge to the fielding of these platforms. Furthermore, the compliant nature of high-speed structures in combination with the extreme environments result in the potential for path-dependent loading conditions and deformed configurations that evolve over long-duration trajectories. While computational fluid dynamics (CFD) provides high accuracy solutions, computational costs limit application for online loads prediction. In contrast, basic engineering-level approximations are efficient but lack broad accuracy. These issues have motivated the development of CFD surrogates that harness the predictive accuracy of high-fidelity models while retaining the computational efficiency required for online predictions. While a significant body of work has demonstrated the capabilities of the CFD surrogate method, open questions remain regarding the viability of the approach for shock-dominated environments and systems with complex structural responses. This dissertation seeks to address these questions through the identification and development of required improvements. Specific tasks include characterizing the accuracy of the CFD surrogate approach for aeroelastic loads prediction in the presence of shock impingements and the development of modeling strategies to account for arbitrary structural deformations. For quasi-steady stationary and oscillating shock impingements, the CFD surrogate yields reasonable to excellent agreement with unsteady CFD at a fraction of the online computational cost. However, the accuracy of the model degrades as the relative length between the shock-induced separation and deformation increases. Through analytical and numerical studies, these e (open full item for complete abstract)

Committee: Jack McNamara (Advisor); Jen-Ping Chen (Committee Member); Sandip Mazumder (Committee Member); Benjamin Smarslok (Committee Member) Subjects: Aerospace Engineering

Doctor of Philosophy, The Ohio State University, 2016, Aero/Astro Engineering

The use of thin-gauge, light-weight structures in combination with the severe aero-thermodynamic loading makes reusable hypersonic cruise vehicles prone to fluid-thermal-structural interactions. These interactions result in surface perturbations in the form of temperature changes and deformations that alter the stability and eventual transition of the boundary layer. The state of the boundary layer has a significant effect on the aerothermodynamic loads acting on a hypersonic vehicle. The inherent relationship between boundary-layer stability, aerothermodynamic loading, and surface conditions make the interaction between the structural response and boundary-layer transition an important area of study in high-speed flows. The goal of this dissertation is to examine the interaction between boundary layer transition and the response of aerothermally compliant structures. This is carried out by first examining the uncoupled problems of: (1) structural deformation and temperature changes altering boundary-layer stability and (2) the boundary layer state affecting structural response. For the former, the stability of boundary layers developing over geometries that typify the response of surface panels subject to combined aerodynamic and thermal loading is numerically assessed using linear stability theory and the linear parabolized stability equations. Numerous parameters are examined including: deformation direction, deformation location, multiple deformations in series, structural boundary condition, surface temperature, the combined effect of Mach number and altitude, and deformation mode shape. The deformation-induced pressure gradient alters the boundary-layer thickness, which changes the frequency of the most-unstable disturbance. In regions of small boundary-layer growth, the disturbance frequency modulation resulting from a single or multiple panels deformed into the flowfield is found to improve boundary-layer stability and potentially delay transition. For (open full item for complete abstract)

Committee: Jack McNamara (Advisor); Jeffrey Bons (Committee Member); Datta Gaitonde (Committee Member); Sandip Mazumder (Committee Member); Benjamin Smarslok (Committee Member); S. Michael Spottswood (Committee Member) Subjects: Aerospace Engineering