Characteristics of Hypersonic Wing-Elevon-Cove Flows
Abstract
Hypersonic flight vehicle development heavily relies on continued research focused on hypersonic flows. The prediction of aerothermodynamic loading, i.e., surface pressure and heat transfer, under flight conditions is a fundamental design requirement. However, hypersonic flight involves severe flowfield environments and complex flow phenomena which require specific experimental considerations or the use of computational fluid dynamics to accurately characterize. The Reynolds numbers and Mach numbers in hypersonic flight are high, and the hypersonic regime is generally associated with large levels of aerothermodynamic loading. Shock-wave/boundary-layer interactions also occur near flight vehicle surfaces, such as leading-edges and control surfaces. These interactions have a significant influence on vehicle performance and introduce large-scale flow separation, unsteadiness, and increased aerothermodynamic loading. The low-frequency behavior of the unsteady shock-motion is a concern for hypersonic flight vehicles because the oscillations produce prolonged fluctuations of intense aerothermodynamic loadings and can lead to structure failure. Therefore, research on shock-wave/boundary-layer interactions has clear practical applications in the development of hypersonic flight vehicles, and by studying their characteristics, a better understanding of fundamental design requirements can be obtained. These interactions are strongly determined by the local geometry of the flight vehicle. Small physical deviations from smooth aerodynamic surfaces can significantly affect the flowfield and resultant aerothermodynamic loading. Most studies focused on hypersonic flows, however, employ simplified surface geometries as a necessary requirement to facilitate the experiment. This routine idealization leads to overlooking geometric imperfections and ignoring their effects on the local flowfield, which introduces discrepancies between experimental and flight parameters. Relevant geometric imperfections encompass any deviations from a smooth aerodynamic surface, such as roughness, steps, gaps, and cavities. Hypersonic gaps have limited available research and are prevalent on flight vehicles. Gaps found near control surfaces are large enough to significantly alter the flow structure, shock-wave/boundarylayer interaction, and aerothermodynamic loading. A need therefore exists for investigation of geometric imperfections in hypersonic flight, specifically for gaps and cavities. This dissertation covers a computational investigation into hypersonic flight vehicle geometric imperfections, with a focus on wing-elevon-cove configurations. The primary region of focus for the overall research was the cove region at the juncture of the main wing element and the elevon. This region is associated with the shock-wave/boundary-layer interaction produced by the control surface deflection. There also exists a centrifugal instability at the cove, due to streamline curvature, which is associated with the production of Görtler vortices. The content includes three projects revolving around hypersonic wing-elevon-cove flows. These flows were computed with improved delayed detached-eddy simulation. The first project was a computational investigation simulating the NASA experimental study done by W.D. Deveikis and W. Bartlett in 1978. This experiment consisted of hypersonic high Reynolds number wind tunnel tests for a shuttle-type reentry vehicle. The computational aerothermodynamic surface loadings for this project were compared to the experimental published data. Grounded with the agreement with mean surface data, this project expanded on the topics explored in the experimental study to include topics such as flow visualization and statistical analysis.
Degree
Ph.D.
Advisors
Blaisdell, Purdue University.
Subject Area
Theoretical physics
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