Slat noise aeroacoustic experiments in closed-section wind-tunnel

• Autor(a) principal: Filipe Ramos do Amaral
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://doi.org/10.11606/T.18.2020.tde-15012020-165231

Slat noise is an important research topic regarding the design of quieter aircraft. The noise generation mechanisms of a slat device are still not well understood and experiments with simplified scaled models at low-speed closed-section wind-tunnels are among the standard tools for the study of such an issue. This doctoral thesis reports on an extensive experimental database on slat noise of a scaled two-dimensional unswept and untapered MD30P30N high-lift model and addresses several issues regarding slat noise experiments. Conventional beamforming, DAMAS and CLEAN-SC deconvolution techniques were employed for the post-processing of acoustic data, although such methodologies cannot always reconstruct the line source pattern map correctly. An investigation on beamforming methodologies and their ability to represent a line source and its spectral level estimates was conducted for a synthetic line source and a physical one. An original variation of the beamforming cluster approach based on the coherence level amongst microphone pairs was introduced and improved the results. Pressure taps were used in the assessment of spanwise and chordwise pressures on the high-lift airfoil model surfaces. The wind-tunnel wall effects were also addressed and included studies on working section side-wall suction for mitigating the three-dimensionalities resulting from the interaction of the tunnel wall boundary-layer with the model-ends and a foam coating acoustic treatment applied to the tunnel walls towards weakening the mirror sources caused by reverberation. The experimental database includes a wide range of angles of attack (from -6 deg up to the stall, approximately at 18 deg) and Mach numbers (0.07 to 0.1), which corresponds to an approximately 7 × 105 to 106 Reynolds number range, for three distinct slat geometrical configurations - the original MD30P30N, another with a higher slat deflection and one with smaller slat gap and overlap. A two-dimensional excrescence was installed on the slat cove surface and represents a sealing device. Nine seal positions along the slat cove wall and six different seal cross-sections were tested for 3 to 9 deg angles of attack and 0.1 Mach number. Finally, a circular phased array design for nearfield aeroacoustic measurements in small closed-section wind-tunnels was introduced and can be employed for slat noise experiments.