On the Adjoint-based Control of Trailing-Edge Turbulence and Noise Minimization via Porous Material

Zhou, Beckett Yx; Gauger, Nicolas R.; Koh, Seong Ryong; Meinke, Matthias; Schröeder, Wolfgang

doi:10.2514/6.2015-2530

Cited by 9 publications

(3 citation statements)

References 14 publications

(12 reference statements)

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“…Numerical computations by Bae & Moon [15] corroborate these trends, demonstrate the ability of porous trailing edges to suppress tonal peaks in the acoustic signature, and suggest that the optimization of the porosity distribution could enable greater noise reductions (e.g. [16]). Hence, there is a potential trade-off between the acoustical benefits of porosity and its negative impact on aerodynamic performance.…”

Section: Introductionmentioning

confidence: 83%

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: 83%

The steady aerodynamics of aerofoils with porosity gradients

Hajian¹,

Jaworski²

2017

Proc. R. Soc. A.

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“…There are also approaches to combine the successful concept of serrated trailing edges with a porous modification [11]. In addition, there are a variety of analytical [12] and numerical studies [13][14][15][16] on porous trailing edges for noise reduction available.…”

Section: Introductionmentioning

confidence: 99%

Self Noise Reduction and Aerodynamics of Airfoils with Porous Trailing Edges

Geyer

Sarradj

2019

Acoustics

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The application of open-porous materials is a possible method to effectively reduce the aerodynamic noise of an airfoil. However, the porous consistency may have a negative effect on the aerodynamic performance of the airfoil, since very often the lift is decreased while the drag increases. In a recent investigation, the generation of trailing edge noise of a set of airfoil models made from different porous materials was examined experimentally. The materials were characterized mainly by their airflow resistivity. Besides the material, the chordwise extent of the porous material was varied, which was done by covering the front part of the porous airfoil with a thin, impermeable adhesive foil. Acoustic measurements were performed in an open jet wind tunnel using microphone array technology, while the aerodynamic performance was measured simultaneously using a six-component balance. In general, both the airflow resistivity and the extent of the porous material have an influence on the trailing edge noise. However, if a suitable material is chosen, the results show that a noticeable reduction of trailing edge noise is possible even with only a small chordwise extent of the porous material.

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“…Koh et al (2014) performed numerical simulations based on LES and acoustic perturbation equations (APE) on the possibility of bluntness noise reduction and found that the use of porous trailing-edges can reduce the sound pressure level at the fundamental vortex shedding frequency by 10 dB and the overall sound pressure level in the range of 3-8 dB. In addition, Zhou et al (2015) developed an LES-based discrete adjoint-based optimization framework to obtain the optimal distribution of porous materials on trailing-edge of a flat plate. More recently, Koha et al (2017) performed an LES-based computational study on the impact of porous surfaces on trailing-edge noise and showed that the implementation of porous trailing-edge can lead to a reduction of the overall sound pressure by up to 11 dB in the case of a flat plate at zero angle-of-attack.…”

Section: Introductionmentioning

confidence: 99%

Trailing-edge flow and noise control using porous treatments

2018

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This paper is concerned with the application of porous treatments as a means of flow and aerodynamic noise reduction. An extensive experimental investigation is undertaken to study the effects of flow interaction with porous media, in particular in the context of the manipulation of flow over blunt trailing edges and attenuation of vortex shedding. Comprehensive boundary layer and wake measurements have been carried out for a long flat plate with solid and porous blunt trailing edges. Unsteady velocity and surface pressure measurements have also been performed to gain an in-depth understanding of the changes to the energy–frequency content and coherence of the boundary layer and wake structures as a result of the flow interaction with a porous treatment. Results have shown that permeable treatments can effectively delay the vortex shedding and stabilize the flow over the blunt edge via mechanisms involving flow penetration into the porous medium and discharge into the near-wake region. It has also been shown that the porous treatment can effectively destroy the spanwise coherence of the boundary layer structures and suppress the velocity and pressure coherence, particularly at the vortex shedding frequency. The flow–porous scrubbing and its effects on the near-wall and large coherent structures have also been studied. The emergence of a quasi-periodic recirculating flow field inside highly permeable surface treatments has also been investigated. Finally, the paper has identified several important mechanisms concerning the application of porous treatments for aerodynamic and aeroacoustic purposes, which can help more effective and tailored designs for specific applications.

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On the Adjoint-based Control of Trailing-Edge Turbulence and Noise Minimization via Porous Material

Cited by 9 publications

References 14 publications

The steady aerodynamics of aerofoils with porosity gradients

The steady aerodynamics of aerofoils with porosity gradients

Self Noise Reduction and Aerodynamics of Airfoils with Porous Trailing Edges

Trailing-edge flow and noise control using porous treatments

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