Experimental and Analytical Investigation of the Distortion of Turbulence Interacting with a Porous Airfoil

Zamponi, Riccardo; Schram, Christophe; Moreau, Stéphane; Ragni, Daniele

doi:10.2514/6.2021-2289

Cited by 1 publication

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References 49 publications

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“…In addition, large-eddy simulations (LES) for this experimental setup were carried out by Satcunanathan et al [27] to shed additional light upon the flow-field alterations caused by porosity. Both measurements and numerical computations were further analyzed by Zamponi et al [28,29], who identified the milder distortion experienced by the largest turbulent eddies as one of the prevalent noise-mitigation mechanisms related to the porous treatment of the wing profile. This link was subsequently confirmed by Tamaro et al [30] with particle image velocimetry and acoustic far-field measurements.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Curle's Dipolar Sources on a Porous Airfoil Interacting with Incoming Turbulence

Zamponi

Satcunanathan

Moreau

et al. 2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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Integrating porous materials into the structure of an airfoil constitutes a promising passive strategy for mitigating the noise from turbulence-body interactions that has been extensively explored in the past few decades. When a compact permeable body is considered in the aeroacoustic analogy derived by Curle to predict this noise source, a dipole associated with the nonzero unsteady Reynolds stresses appears on the surface in addition to the dipole linked to the pressure fluctuations. Nevertheless, the relative contribution of this source on the far-field noise radiated by a porous wing profile has not been clarified yet. The purpose of the current research work is twofold. On the one hand, it investigates the impact of porosity on the surface-pressure fluctuations of a thick airfoil immersed in the wake of an upstream circular rod at a Mach number of 0.09. On the other hand, it quantifies the relevance of the Reynolds-stresses term on the surface as a sound-generation mechanism. Results from large-eddy simulations show that the porous treatment of the wing profile yields an attenuation of the unsteady-pressure peak, which is localized in the low-frequency range of the spectrum and is induced by the milder distortion of the incoming vortices. However, porosity is ineffective in breaking the spanwise coherence or in-phase behavior of the surface-pressure fluctuations at the vortex-shedding frequency. The Reynolds-stresses term is found to be considerable in the stagnation region of the airfoil, where the transpiration velocity is larger, and partly correlated with the unsteady surface pressure. This results in a nonnegligible contribution of this term to the far-field acoustic pressure emitted by the porous wing profile for observation angles near the stagnation streamline. The conclusions drawn in the present study eventually provide valuable insight into the design of innovative and efficient passive strategies to mitigate surface-turbulence interaction noise in industrial applications.

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