On the attenuating effect of permeability on the low frequency sound of an airfoil

Weidenfeld, M.; Manela, A.

doi:10.1016/j.jsv.2016.04.002

Cited by 10 publications

(8 citation statements)

References 34 publications

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“…The aforementioned works consider only stationary bodies and represent porosity with the Rayleigh conductivity of a thin perforated surface, which neglects any viscous effects within the pores. Weidenfeld & Manela [11] predicted that porous noise reductions can indeed persist when a viscous Darcy porosity condition is applied to a pitching aerofoil. However, to be useful in the design of any practical application, these aeroacoustic works need a complementary assessment of porosity on the aerodynamics.…”

Section: Introductionmentioning

confidence: 99%

The steady aerodynamics of aerofoils with porosity gradients

Hajian¹,

Jaworski²

2017

Proc. R. Soc. A.

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This theoretical study determines the aerodynamic loads on an aerofoil with a prescribed porosity distribution in a steady incompressible flow. A Darcy porosity condition on the aerofoil surface furnishes a Fredholm integral equation for the pressure distribution, which is solved exactly and generally as a Riemann-Hilbert problem provided that the porosity distribution is Hölder-continuous. The Hölder condition includes as a subset any continuously differentiable porosity distributions that may be of practical interest. This formal restriction on the analysis is examined by a class of differentiable porosity distributions that approach a piecewise, discontinuous function in a certain parametric limit. The Hölder-continuous solution is verified in this limit against analytical results for partially porous aerofoils in the literature. Finally, a comparison made between the new theoretical predictions and experimental measurements of SD7003 aerofoils presented in the literature. Results from this analysis may be integrated into a theoretical framework to optimize turbulence noise suppression with minimal impact to aerodynamic performance.

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Section: Introductionmentioning

confidence: 99%

The steady aerodynamics of aerofoils with porosity gradients

Hajian¹,

Jaworski²

2017

Proc. R. Soc. A.

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“…More precisely, the sound is generated by the complex vortices and their interactions around the flapping wings that include three main vortices: leading edge vortex, trailing edge vortex and wing tip vortex [19][20][21]. The dominating sound sources are expected to be of a dipole type consisting of a) the wings motion, b) the vortex-structure interactions, and c) permeability [22].…”

mentioning

confidence: 99%

Bioinspired Low-Noise Wing Design for a Two-Winged Flapping-Wing Micro Air Vehicle

Debiasi

Nguyen

et al. 2018

AIAA Journal

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“…However, caution should be exercised in the large-frequency limit, which is beyond the realm of physical validity of the mathematical modelling employed in this paper: as discussed by Howe (1979) and noted more recently by Weidenfeld & Manela (2016), the present modelling assumptions for porosity are only valid when there is Stokes flow in the pores passing through the wing, which is rendered invalid at large frequencies. We expect that a higher-order (e.g.…”

Section: Porous Extensions Of Standard Unsteady Aerodynamic Functionsmentioning

confidence: 93%

“…The expansion of the jump in surface pressure across the aerofoil into a series of weighted Chebyshev polynomials has previously been applied to aerodynamic problems for impermeable (Rienstra 1992) and permeable (Weidenfeld & Manela 2016) aerofoils. The weighted Chebyshev expansion (also referred to as a Glauert–Fourier series) is an essential feature of many reduced-order discrete-vortex models (Ramesh et al.…”

Section: Introductionmentioning

confidence: 99%