Airfoil-Turbulence Interaction Noise Source Identification and its Reduction by Means of Leading Edge Serrations

Bampanis, Georgios; Roger, Michel; Ragni, Daniele; Avallone, Francesco; Teruna, Christopher

doi:10.2514/6.2019-2741

Cited by 18 publications

(32 citation statements)

References 20 publications

(34 reference statements)

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“…The tip plane of the rear serrated airfoil exhibits a fundamentally different behavior possibly due to the emergence of counter-rotating vortices from the tip (tip flow), as previously observed through PIV Q5 measurements. 40,41 The serration tip plane measures the impact of Phys. Fluids 32, 000000 (2020); doi: 10.1063/5.0012958 32, 000000-9…”

Section: Unsteady Surface Pressurementioning

confidence: 99%

On the use of leading-edge serrations for noise control in a tandem airfoil configuration

et al. 2020

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Passive noise control for a tandem NACA 65-710 airfoil configuration is experimentally investigated by applying leading-edge serrations on the rear airfoil. With a sliding side-plate mechanism that allows the rear airfoil to move in the vertical direction relative to the front airfoil, the position of maximum turbulence interaction noise is first identified from the far-field noise measurements. Subsequently, detailed static surface pressure distribution and unsteady surface pressure fluctuations are acquired to shed more light on the physical phenomenon and underlying noise-reduction mechanism of the leading-edge serrations. The far-field noise measurements confirm that a notable turbulence interaction noise reduction can be achieved from 600 Hz < f < 3000 Hz, agreeing well with the previous literature on the effectiveness of the leading-edge serrations. The near-field hydrodynamic analyses obtained using remote-sensing techniques of the fluctuating pressure fields over the airfoil show that a significant reduction in the surface pressure fluctuation levels up to 20 dB/Hz can be observed at the serrated-tip plane of the rear serrated airfoil close to the leading-edge regions, over the range of frequencies investigated. Although reduction can also be observed on the serrated-root plane, the magnitude is much less significant. The present results suggest that the modification of the unsteady loading on the rear airfoil by the leading-edge serrations plays a crucial role in the reduction of turbulence interaction noise in the tandem airfoil configuration, which may find practical application for noise reduction in aerodynamic systems involving rows of airfoils, such as contra-rotating open rotors and outlet guide vanes.

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Section: Unsteady Surface Pressurementioning

confidence: 99%

On the use of leading-edge serrations for noise control in a tandem airfoil configuration

et al. 2020

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“…In recent years there has been considerable interest in the use of leading edge (LE) serrations aimed at reducing interaction noise [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. However, most of these papers were focused on single-wavelength serrated leading edge profiles.…”

Section: A Single-wavelengthmentioning

confidence: 99%

Leading-Edge Profiles for the Reduction of Airfoil Interaction Noise

2020

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Aerofoils operating in a turbulent flow are an efficient source of noise radiation by scattering vorticity into sound at the leading edge. Much work has been undertaken demonstrating the effectiveness by which serrations, or undulations, introduced onto the leading edge, can substantially reduce broadband leading edge interaction noise. However, most of this work is focused on sinusoidal leading edge serration profiles. In this paper, a family of serration profiles are proposed that are capable of providing significantly greater noise reductions than single-wavelength serrations at optimal conditions. This new family of profiles will be shown to reduce interaction noise through a fundamentally different noise reduction mechanism than conventional single-wavelength profiles. Unlike single-wavelength profiles, which produce a single compact dominant source region per serration wavelength, these new profiles are designed to produce two or more dominant compact sources per serration wavelength of roughly the same source strength, that are separated in the streamwise direction. Since these sources are arranged to be closer together than the turbulence length-scale, they are highly coherent and, at certain frequencies, radiate exactly 180 • out of phase leading to very high levels of noise reduction in the far field. The experimental noise reduction spectra are compared against an analytic model obtained as a solution of the acoustic wave equation using the Wiener-Hopf technique. This is shown to be unable to capture the main features of the noise reduction spectra as the source strength distribution for other profiles are not captured. A simple model has therefore been developed to explain the noise reduction mechanism for these new profiles, based on interference between sources distributed along the leading edge. Good qualitative agreement is obtained with the experimental results. * Research fellow, ccp1m17@soton.ac.uk † Professor, Senior member AIAA, pfj@soton.ac.uk ‡ EPSRC research fellow, member AIAA, lja30@cam.ac.uk

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“…While conducting acoustic tunnel measurements, Amiet [8] observed that the grid-generated turbulence approached the condition of isotropic turbulence in the test section of the tunnel, with a good agreement with von Kármán spectrum model. This near isotropic condition was, however, achieved in the absence of the airfoil in the test chamber of the acoustic tunnel, and it has been replicated in several studies such as in Devenport et al [10], Bampanis et al [11] and Juknevicius and Chong [12].…”

Section: Introductionmentioning

confidence: 61%

A rapid distortion theory-based airfoil turbulent inflow noise prediction method

Faria

Saab

Rodríguez

et al. 2020

J Braz. Soc. Mech. Sci. Eng.

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Turbulent inflow (TI) noise is reported as an important source of wind turbine (WT) broadband aeroacoustic noise, coexistent with many other sources (e.g., the airfoil self-noise). This manuscript intends to elucidate the discussion on TI noise by providing an alternative prediction method based on the rapidly distorted anisotropic turbulent velocity energy spectrum. A review on turbulent inflow noise prediction is presented, followed by the discussion on turbulence modeling and the derivation of a modified TI noise prediction expression, which allows a more detailed assessment of wind turbine noise sources. This can contribute for WT blade optimization, once it is implemented in design codes that consider noise as a constraint. Criteria for the turbulent velocity spectrum to be characterized by the rapid distortion theory (RDT) are established, and the validation methodology is carried through comparisons between the novel semi-empirical prediction method and data gathered from recent literature for a flat-plate airfoil with 3% relative thickness and a NACA 0008 airfoil. The RDT-modified turbulent inflow noise prediction method shows better agreement with the measured data, when compared to predictions that adopt an isotropic model for the turbulent velocity energy spectrum, a condition only achieved in the absence of the airfoil in the test section of aeroacoustic facilities.

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Airfoil-Turbulence Interaction Noise Source Identification and its Reduction by Means of Leading Edge Serrations

Cited by 18 publications

References 20 publications

On the use of leading-edge serrations for noise control in a tandem airfoil configuration

On the use of leading-edge serrations for noise control in a tandem airfoil configuration

Leading-Edge Profiles for the Reduction of Airfoil Interaction Noise

A rapid distortion theory-based airfoil turbulent inflow noise prediction method

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