Extensions and limitations of analytical airfoil broadband noise models

Roger, Michel; Moreau, Stéphane

doi:10.1260/1475-472x.9.3.273

Cited by 140 publications

(111 citation statements)

References 40 publications

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“…The effects of variations in aerofoil geometry such as angle of attack, aerofoil thickness, camber, etc, on ATI noise have been studied by Atassi et al (1990), Lockard & Morris (1998), Evers & Peake (2002), Devenport et al (2010), Roger & Moreau (2010), Roger & Carazo (2010), Gill et al (2013), Ayton & Peake (2013) and . Most of this work has been based on two-dimensional turbulence or harmonic vortical gusts at low freestream Mach numbers.…”

Section: Introductionmentioning

confidence: 99%

On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges

2016

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An aerofoil leading-edge profile based on wavy (sinusoidal) protuberances/tubercles is investigated to understand the mechanisms by which they are able to reduce the noise produced through the interaction with turbulent mean flow. Numerical simulations are performed for non-lifting flat-plate aerofoils with straight and wavy leading edges (denoted by SLE and WLE, respectively) subjected to impinging turbulence that is synthetically generated in the upstream zone (freestream Mach number of 0.24). Full threedimensional Euler (inviscid) solutions are computed for this study thereby eliminating self-noise components. A high-order accurate finite-difference method and artefact-free boundary conditions are used in the current simulations. Various statistical analysis methods, including frequency spectra, are implemented to aid the understanding of the noise-reduction mechanisms. It is found with WLEs, unlike the SLE, that the surface pressure fluctuations along the leading edge exhibit a significant source cut-off effect due to geometric obliqueness which leads to reduced levels of radiated sound pressure. It is also found that there exists a phase interference effect particularly prevalent between the peak and the hill centre of the WLE geometry, which contributes to the noise reduction in the mid-to high-frequency range.

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Section: Introductionmentioning

confidence: 99%

On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges

2016

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“…Over the years many approaches have been adopted for the study of ATI noise to understand both the physical noise generation mechanisms and the influence of various geometric parameters such as aerofoil thickness, angle of attack and camber. This includes the theoretical model of Amiet (1975) and its subsequent extensions, namely, the convection of two-dimensional frozen turbulence in a uniform mean flow (Roger & Moreau 2010); theoretical and numerical approaches based on harmonic gusts (Goldstein 1978;Atassi et al 1990;Myers & Kerschen 1995, 1997Lockard & Morris 1998;Evers & Peake 2000;Gill et al 2013;Ayton & Peake 2013; experimental approaches based on grid generated homogeneous isotropic turbulence (Paterson & Amiet 1976;Moreau et al 2005;Devenport et al 2010); and, recent computational approaches based on twoor three-dimensional Euler and Navier-Stokes simulations (Christophe et al 2007(Christophe et al , 2008; Deniau et al 2011;Gill et al 2015;.…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic source mechanisms of a wavy leading edge undergoing vortical disturbances

Turner

Kim

2016

J. Fluid Mech.

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High-accuracy numerical simulations are performed to study aeroacoustic source mechanisms of wavy leading edges (WLE) on a thin aerofoil undergoing vortical disturbances. This canonical study is based on a prescribed spanwise vortex travelling downstream and creating secondary vortices as it passes through the aerofoil's leading edge. The primary aim of the study is to precisely understand the relationships between the vortexinduced velocity perturbation and the wall pressure fluctuation on the WLE geometry. It is observed that by increasing the size (amplitude) of the WLE the source strength at the peak region is reduced rapidly to a certain point and followed by a saturation stage, while at the root (trough) it remains fairly consistent regardless of the WLE size. This observation is demonstrated to be the consequence of three-dimensional vortex dynamics taking place along the WLE. One of the most profound features is that a system of horseshoe-like secondary vortices are created from the WLE peak region upon the impingement of the prescribed vortex. It is found that the horseshoe vortices produce significantly non-uniform velocity perturbation in front of the WLE leading to the disparity in the source characteristics between the peak and root. The alterations to the impinging velocity perturbation are carefully analysed and related to the wall pressure fluctuation in this study. In addition, a semi-analytic model based on Biot-Savart's law is developed to better understand and explain the role of the horseshoe vortex systems and the source mechanisms.

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“…Aerofoils operating in such conditions can be found in micro-wind turbines as well as in compressors, cooling fans and other rotating machinery (Wright 1976;Arcondoulis et al 2010). While self-noise generated by aerofoils at high Reynolds numbers in an undisturbed flow and in the absence of † Email address for correspondence: s.probsting@tudelft.nl separation is dominated by the interaction of the turbulent boundary layers with the trailing edge (Roger & Moreau 2010), tones produced at moderate Reynolds numbers are often associated with the growth and convection of unstable waves in the laminar boundary layer (Arbey & Bataille 1983). …”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of aerofoil tonal noise generation

2014

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The present study investigates the mechanisms associated with tonal noise emission from a NACA 0012 aerofoil at moderate incidence (0• and 4• angle of attack) and with Reynolds numbers ranging from 100 000 to 270 000. Simultaneous time-resolved particle image velocimetry (PIV) of the aeroacoustic source region near the trailing edge and acoustic measurements in the far field are performed in order to establish the correspondence between the flow structure and acoustic emissions. Results of these experiments are presented and analysed in view of past research for a number of selected cases. Characteristics of the acoustic emission and principal features of the average flow field agree with data presented in previous studies on the topic. Time-resolved analysis shows that downstream convecting vortical structures, resulting from growing shear layer instabilities, coherently pass the trailing edge at a frequency equal to that of the dominant tone. Therefore, the scattering of the vortical structures and their associated wall pressure fluctuations are identified as tone generating mechanisms for the cases investigated here. Moreover, wavelet analysis of the acoustic pressure and velocity signals near the trailing edge show a similar periodic amplitude modulation which is associated with multiple tonal peaks in the acoustic spectrum. Periodic amplitude modulation of the acoustic pressure and velocity fluctuations on the pressure side are also observed when transition is forced on the suction side, showing that pressure-side events alone can be the cause.

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Extensions and limitations of analytical airfoil broadband noise models

Cited by 140 publications

References 40 publications

On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges

On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges

Aeroacoustic source mechanisms of a wavy leading edge undergoing vortical disturbances

Experimental investigation of aerofoil tonal noise generation

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