Print Email Facebook Twitter On the role of turbulence distortion on leading-edge noise reduction by means of porosity Title On the role of turbulence distortion on leading-edge noise reduction by means of porosity Author Zamponi, R. (von Karman Institute for Fluid Dynamics) Satcunanathan, S. (Rheinisch-Westfälische Technische Hochschule) Moreau, S. (University of Sherbrooke) Ragni, D. (TU Delft Wind Energy) Meinke, M. (Rheinisch-Westfälische Technische Hochschule) Schröder, W. (Rheinisch-Westfälische Technische Hochschule) Schram, C. (von Karman Institute for Fluid Dynamics) Date 2020 Abstract A possible strategy for the reduction of the aeroacoustic noise generated by turbulence interacting with a wing profile, also referred to as leading-edge noise, is represented by the implementation of a porous medium in the structure of the airfoil. However, the physical mechanisms involved in this noise mitigation technique remain unclear. The present work aims at elucidating these phenomena and particularly how the porosity affects the incoming turbulence characteristics in the immediate vicinity of the surface. A porous NACA-0024 profile equipped with melamine foam has been compared with a solid baseline, both airfoils being in turn subjected to the turbulence shed by an upstream circular rod. The mean wall-pressure distribution along the airfoils shows that the implementation of the porous material mostly preserves the integrity of the NACA-0024 profile's shape. Results of hot-wire anemometry and large-eddy simulations indicate that the porous design proposed in this study allows for a damping of the velocity fluctuations and it has a limited influence on the upstream mean flow field. Specifically, the upwash component of the root-mean-square of the velocity fluctuations turns out to be significantly attenuated in the porous case in contrast to the solid one, leading to a strong decrease of the turbulent kinetic energy in the stagnation region. Furthermore, the comparison between the power spectral densities of the incident turbulent velocities demonstrates that the porosity has an effect mainly on the low-frequency range of the turbulent velocity power spectrum. This evidence is in line with the results of the acoustic beamforming measurements, which exhibit a noise abatement in an analogous frequency range. On the basis of these observations, an interpretation of the phenomena occurring in the turbulence-interaction noise reduction due to a porous treatment of the airfoil is finally given with reference to the theoretical inputs of the Rapid Distortion Theory. Subject Porous materialsRapid distortion theoryRod-airfoil configurationTurbulence-interaction noise To reference this document use: http://resolver.tudelft.nl/uuid:a4920bc4-b51b-456f-abd1-d6882ac43863 DOI https://doi.org/10.1016/j.jsv.2020.115561 ISSN 0022-460X Source Journal of Sound and Vibration, 485 Part of collection Institutional Repository Document type journal article Rights © 2020 R. Zamponi, S. Satcunanathan, S. Moreau, D. Ragni, M. Meinke, W. Schröder, C. Schram Files PDF 1_s2.0_S0022460X2030393X_main.pdf 4.41 MB Close viewer /islandora/object/uuid:a4920bc4-b51b-456f-abd1-d6882ac43863/datastream/OBJ/view