A CAA Study of Turbulence Distortion in Broadband Fan Interaction Noise

Hainaut, Thomas; Gabard, Gwénaël; Clair, Vincent

doi:10.2514/6.2016-2839

Cited by 9 publications

(8 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The transverse turbulence spectrum is increased at low frequencies and decreased at high frequencies, whereas the spanwise turbulence spectrum follows the opposite trend. The behaviour of the distorted E 22 in the root region, which is the dominant turbulence spectrum on the leading edge noise of a flat plate, 21 is similar to that reported by Gea-Aguilera et al 23 and Hainaut et al 34 in the vicinity of two-dimensional thick airfoils. There are significant differences between the distortion of the turbulence spectra at the peak and root regions of a wavy leading edge airfoil.…”

Section: Via Distortion Of Turbulent Structures and Velocity Spectrasupporting

confidence: 80%

“…32 The present study also examines the distortion of the velocity spectra in the vicinity of the airfoil with wavy leading edge, as this has been highlighted as a key factor in turbulence-airfoil interaction noise. 23,33,34 Table 1. Length scales of anisotropic turbulence to study the effect of lx/hw and lz/λw in the noise generation mechanism of airfoils with wavy leading edge.…”

Section: Peak Cross-sectionmentioning

confidence: 99%

“…The distortion of the turbulent structures in the leading edge region is believed to be responsible for the noise reduction of thick airfoils at high frequencies. Previous works examined the distortion of harmonic gusts 32,35 and isotropic turbulence 23,34 in two-dimensional CAA simulations of isolated airfoils. Additionally, experiments of airfoils with straight leading edge have also been performed to study the turbulent flow features in the leading edge region.…”

Section: Via Distortion Of Turbulent Structures and Velocity Spectramentioning

confidence: 99%

See 2 more Smart Citations

Wavy Leading Edge Airfoils Interacting with Anisotropic Turbulence

Aguilera

Gill

Angland

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

Leading edge noise reductions caused by serrations have been shown to be sensitive to the length scales of vortical disturbances. In order to improve the understanding of wavy leading edge airfoils as a noise reduction technology, this paper examines the effects of anisotropy on turbulence-airfoil interaction noise by means of computational aeroacoutic simulations. A synthetic turbulence method is used to generate fully three-dimensional, divergence-free, homogeneous anisotropic turbulence, which is injected in a linearized Euler equation solver to model the noise generation. Moderate variations in turbulence length scales, which are representative of the anisotropy in aero-engine fan wakes, are tested for a NACA 0012 airfoil with a wavy leading edge. This work focuses on the noise sources in the near-field by examining the distortion of the turbulent structures and velocity spectra in the vicinity of the noise sources, the unsteady pressure and its spectral density on the airfoil surface, the magnitude-squared coherence between velocity and pressure fluctuations on the noise sources, and the correlation between noise sources along the span for various degrees of anisotropy. Numerical results show that small variations in the turbulence length scales can produce significant changes in the spectral content of the noise sources at the peak and root regions. The loudest noise source is always located in the root region for the cases examined and this source is mainly affected by the transverse velocity fluctuations. To reduce the correlation between noise sources in the peak and root regions, the ratio between the chordwise length scale and the amplitude of the serrations, and the ratio between the spanwise length scale and the wavelength of the leading edge should satisfy lx/(2hw) < 1 and lz/λw ≤ 0.5, respectively.Recent experimental, numerical, and analytical studies 6,8,14,15 highlighted the importance of the length scales of the vortical disturbances or turbulence as a key parameter in the noise reduction of wavy leading edge airfoils. However, the majority of previous works were based on the flat plate assumption 8, 16 and used simplified representations for the turbulence, such as harmonic gusts 14 or isotropic turbulence. 8 Unlike previous works that focused on flat plates and isotropic turbulence, the present work studies the noise generation mechanisms of an airfoil with wavy leading edge in the presence of anisotropic turbulence. Although the effects of anisotropic turbulence have been shown to be limited in airfoils with straight leading edge, 17 wavy leading edge airfoils are expected to be more sensitive to anisotropic turbulence due to additional three-dimensional mechanisms caused by the amplitude and wavelength of the leading edge serrations. In this work, Computational AeroAcoustic (CAA) simulations are performed by means of a synthetic turbulence method to generate fully three-dimensional anisotropic turbulence and a linearized Euler equation (LEE) solver for the noise generation. The following top...

show abstract

Section: Via Distortion Of Turbulent Structures and Velocity Spectrasupporting

confidence: 80%

Section: Peak Cross-sectionmentioning

confidence: 99%

Section: Via Distortion Of Turbulent Structures and Velocity Spectramentioning

confidence: 99%

See 1 more Smart Citation

Wavy Leading Edge Airfoils Interacting with Anisotropic Turbulence

Aguilera

Gill

Angland

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

show abstract

“…This turns out to be computationally intensive. A more efficient solution consists in empirically weighting Gaussian filters with different length scales and amplitudes [17,20]. Wohlbrandt et al [21] have derived analytical weighting functions in order to realize typical isotropic turbulence spectra by superposition of Gaussian spectra.…”

Section: Introductionmentioning

confidence: 99%

Impact of cyclostationarity on fan broadband noise prediction

Wohlbrandt

Kissner

Guérin

2018

Journal of Sound and Vibration

View full text Add to dashboard Cite

One of the dominant noise sources of modern Ultra High Bypass Ratio (UHBR) engines is the interaction of the rotor wakes with the leading edges of the stator vanes in the fan stage. While the tonal components of this noise generation mechanism are fairly well understood by now, the broadband components are not. This calls to further the understanding of the broadband noise generation in the fan stage. This article introduces the cyclostationary stochastic hybrid (CSH) method, which accommodates in-depth studies of the impact of cyclostationary wake characteristics on the broadband noise in the fan stage. The Random Particle Mesh (RPM) method is used to synthesize a turbulence field in the stator domain using a URANS simulation characterized by time-periodic turbulence and mean flow. The rotor-stator interaction noise is predicted by a two-dimensional CAA computation of the stator cascade. The impact of cyclostationarity is decomposed into various effects investigated separately. This leads to the finding that the periodic turbulent kinetic energy (TKE) and periodic flow have only a negligible effect on the radiated sound power. The impact of the periodic integral length scale (TLS) is, however, substantial. The limits of a stationary representation of the TLS are demonstrated making the CSH method indispensable when background and wake TKE are of comparable level. Good agreement of the CSH method with measurements obtained from the 2015 AIAA Fan Broadband Noise Prediction Workshop are also shown.

show abstract

“…More recent analytic (Ayton (2016)), numerical (Hainaut et al (2016)) and experimental studies (Chaitanya et al (2015a)) were conducted to understand the influence of nose radius, thickness, maximum thickness location, chord etc on radiated noise. The summary of the results are as follows:…”

Section: Introductionmentioning

confidence: 99%

Aerofoil geometry effects on turbulence interaction noise

Paruchuri

2015

21st AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

Faculty of Engineering and the Environment Institute of Sound and Vibration Research Doctor of PhilosophyAerofoil geometry effects on turbulence interaction noise by Chaitanya PARUCHURI Fan broadband is one of the dominant noise sources on an aircraft engine, particularly at approach. The dominant noise generation mechanism is due to turbulent-aerofoil interaction noise (TAI). This thesis investigates the effect of changes in 2D aerofoil geometry on TAI noise. The main focus of this thesis is to attempt to reduce it through the development of innovative leading edge geometries. The first two chapters of the thesis deals with an experimental and numerical investigation into the effect of aerofoil geometry on interaction noise on single aerofoils and on cascades. Consistent with previous work, they show that variations in aerofoil parameters, such as aerofoil thickness, leading edge nose radius and camber, produce only a small changes in broadband interaction noise at approach conditions. Subsequent chapters deal with the development of innovative leading edge serration profiles aimed at reducing interaction noise. Chapter 4 is a detailed study into the limitations of single-wavelength serrations in reducing interaction noise. The optimum profile is identified. Chapters 5, 6 and 7 all deal with the development of innovative profiles that can provide up to 10dB of additional noise reductions compared to single-wavelength serrations. For each of the profiles investigated a simple model is developed to aid the understanding of their interaction mechanism. v

show abstract

A CAA Study of Turbulence Distortion in Broadband Fan Interaction Noise

Cited by 9 publications

References 27 publications

Wavy Leading Edge Airfoils Interacting with Anisotropic Turbulence

Wavy Leading Edge Airfoils Interacting with Anisotropic Turbulence

Impact of cyclostationarity on fan broadband noise prediction

Aerofoil geometry effects on turbulence interaction noise

Contact Info

Product

Resources

About