Effect of deflection angle on the noise and aerodynamic loads generated by a wall-mounted flat plate

Parnis, Owen and Angland, David (2023) Effect of deflection angle on the noise and aerodynamic loads generated by a wall-mounted flat plate. In AIAA Aviation and Aeronautics Forum and Exposition, AIAA AVIATION Forum 2023. American Institute of Aeronautics and Astronautics.. (doi:10.2514/6.2023-3493).

Abstract

Inclined flat plates mounted on a planar surface have an application in the aerospace sector, particularly in the form of spoilers. They also have applications in other sectors, including the renewable energy and automotive sectors. Previous studies on inclined finite flat plate shave already shown the effects that the aspect ratio and the distance from the leading edge to the mounting plane have on the aerodynamic loads of the plate. However, the scaling laws for the aerodynamic loads and the noise generated by a wall-mounted inclined plate are yet to be systematically investigated. This paper aims to establish scaling relationships between the aero dynamic loads and noise spectrum for an inclined-mounted flat plate at different deflection angles. In the absence of a high-lift wing, the changes and scaling laws can be attributed to changes in the spoiler itself and not due to the effects it may have on other components. Wind tunnel experiments were performed to determine these relationships for a wall-mounted plate as a function of the deflection angle mounted to a flat base plate. The wall-mounted plate was deflected between a deflection angle of 10° and 90° at 10° intervals at different Reynolds numbers. Results obtained for the normalised normal force coefficient with the projected front alarea show a good collapse of all of the deflection angles except for 10◦. This value is equal to the drag coefficient of a plate when it deflected perpendicular to the flow, i.e. 90°. At very low deflection angles, the flat plate was significantly immersed in the boundary layer, which changes the behaviour. The force data show a Reynolds number independence. No coherent bluff body vortex shedding is observed in the wake of the flat plate in the hot-wire measurements showing that the wake is broadband in nature. A separation bubble is observed upstream of the in clined plate, whose size is a function of the deflection angle. The far-field acoustic scaling laws showed that the noise generated by a flat plate at a given deflection angle scales approximately with the projected frontal area and velocity to the power of six, suggesting that the primary noise source mechanism is a dipole in nature. However, the collapse is not perfect, particularly at higher deflection angles, suggesting other source mechanisms may also contribute. Phased micro phone array measurements showed that edge noise sources have an important contribution.

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Contributors

Author: David Angland

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