Print Email Facebook Twitter Simulating the acoustic response of cavities to improve microphone array measurements in closed test section wind tunnels Title Simulating the acoustic response of cavities to improve microphone array measurements in closed test section wind tunnels Author VanDercreek, Colin (TU Delft Aircraft Noise and Climate Effects) Avallone, F. (TU Delft Wind Energy) Ragni, D. (TU Delft Wind Energy) Snellen, M. (TU Delft Aircraft Noise and Climate Effects) Date 2022 Abstract Cavities placed along wind tunnel walls can attenuate the turbulent boundary layer (TBL) fluctuations as they propagate into the cavity. Placing microphones within the cavities can thus improve the signal-to-noise ratio of acoustic data. However, standing waves form within these cavities distorting the acoustic measurements. This work uses a finite element (FE) solver to evaluate how cavity geometry (depth, diameter, and wall angle) and wall material (hard-walled and melamine foam) affect the amplitude and eigenfrequency of standing waves when excited by an incident acoustic plane wave. Good agreement between predicted and measured acoustic transfer functions is shown. Compared to cylindrical cavities, countersunk and conical cavities improve the overall response, i.e., reducing the quality factor quantifying the resonance and damping characteristics. Stainless steel coverings also reduce the quality factor. A finding is that the shape of the external foam holder rather than the cavity shape drives the standing wave characteristics for the melamine foam cavities. The optimization problem of minimizing the acoustic response while also attenuating the TBL is thus decoupled by using the melamine foam. Consequently, these considerations can be addressed independently by optimizing the outer cavity shape for acoustics and the melamine foam insert for TBL attenuation. To reference this document use: http://resolver.tudelft.nl/uuid:fffc2463-9094-4c14-9261-ea97132a7f8f DOI https://doi.org/10.1121/10.0009274 ISSN 0001-4966 Source The Journal of the Acoustical Society of America, 151 (1), 322-333 Part of collection Institutional Repository Document type journal article Rights © 2022 Colin VanDercreek, F. Avallone, D. Ragni, M. Snellen Files PDF 10.0009274.pdf 4.19 MB Close viewer /islandora/object/uuid:fffc2463-9094-4c14-9261-ea97132a7f8f/datastream/OBJ/view