Liam McQuelin

Abstract:

This research studies the effects of surface pressure distribution and pressure gradient, introduced by the convex surface curvature, on the aeroelastic characteristics of hypersonic aerodynamic surfaces. An inclined trailing-edge flap model cantilevered at the back of a rigid plate is used to form a compression corner configuration. The aeroelastically-deformed convex shape of a planar flap model is taken as a baseline profile and the inclination is changed to obtain different net pressure distributions over the flap compression surface. The higher initial incidence angle of a convex surface leads to a higher pressure gradient near the flap leading-edge and a forward shift in the center of pressure. This study investigates the effects of this surface pressure distribution on the steady-state aeroelastic characteristics of the trailing-edge flap model. The numerical study was performed using the US3D code to generate laminar and turbulent solutions. The computed surface pressure distributions were used to calculate the static deformed shape of the flap. The laminar flow cases showed little difference in deformation of the flap due to a large separated region at the compression corner that resulted in identical pressure distribution regardless of the surface curvature. For the turbulent flow cases, the large pressure gradients near the compression corner changed the aeroelastic deformation of the flap with the introduction of surface curvature. For the same amount of loading, the tip deflection of a convex flap was reduced by approximately 11% in comparison to a planar flap.

Abstract:

This work discusses the design and implementation of close-proximity radiative heaters for aerothermoelastic experiments in short-duration hypersonic facilities. The radiators are employed to selectively heat a compliant panel both to a specific temperature and to impose a prescribed thermal spatial distribution. Analytical and numerical models are used to demonstrate the performance of these radiators. The analytical study shows that the temperature of the test panel is primarily a function of the panel thickness and the proximity of the heater. A 3D finite element study confirmed these predictions and found that reasonable temperature uniformity could be achieved on the compliant panel (∆T < 60 K for Tmax = 550 K) for practical arrangements. FEM simulations also demonstrated that non-uniform temperature distributions can be prescribed on the panel through use of a nonuniform heater but that these distributions are smeared both by thermal conduction in the panel and radiative crosstalk in the panel-heater gap.

Abstract:

Boundary layer transition on a 7-degree half-angle cone at zero angle of attack with varying bluntness is experimentally investigated in cold Mach 6 flow produced by the High Density Tunnel (HDT) at the University of Oxford. The bluntness Reynolds number, ReRN , defined using freestream conditions and the nose radius, is varied over the range 3 × 104 to 1.5 × 106 . The transition Reynolds number, ReXST , increases with ReRN up to approximately ReRN = 8 × 105 . Beyond this value, ReXST exhibits greater variance and a reversal trend with increasing bluntness, consistent with earlier findings by Stetson [1] and Marineau [2]. The boundary and entropy layers are studied simultaneously using high-speed schlieren imaging at 500 kHz. Schlieren images are analysed using a range of spectral techniques, including spectral proper orthogonal decomposition (SPOD) and continuous wavelet transforms (CWT). Coherent waves in the boundary and entropy layers are identified, with dominant frequency peaks ranging from 20 kHz to above 160 kHz. This analysis provides further data on the instabilities and flow structures that may constitute the mechanisms and pathways leading to boundary transition reversal under these conditions.