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Proceedings of the 10th Convention of the European Acoustics Association Forum Acusticum 2023 Politecnico di Torino Torino, Italy September 11 - 15, 2023 |
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Abstract Noise mitigation is critical in the conceptual designs of aircraft. The evolving requirements for noise reduction and the urbanization of aircraft are some reasons why reducing noise is crucial when designing new concepts. Those novel configurations can include complex propulsion-air frame interactions, such as boundary layer ingestion. While research focuses on shrouded solutions, airframe noise mitigation optimization presents a solution for designs that cannot apply shrouding. This paper shows an experimental analysis of surface noise mitigation underneath a propeller under boundary layer ingestion. The propeller is set on the bottom wall of the wind tunnel to generate the boundary layer ingestion. Tripping devices are used to change the boundary layer thicknesses of the flow impinging on the propeller. The noise reduction surfaces are positioned underneath the propeller through a slot on the flat plate. The surface analyzed is a known frequency absorber (quarter-wave resonator) separated from the flow by a Kevlar panel. Two microphone arrays capture the noise coming from the propeller. The results show that the mitigation strategy reduces noise close to the frequencies of interest, but increases the tonal levels of the propeller due to the resonance with the quarter-wave resonators. |