Journal articles: 'Aerofoil Noise'

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Laratro, Alex, Maziar Arjomandi, Benjamin Cazzolato, and Richard Kelso. "Self-noise of NACA 0012 and NACA 0021 aerofoils at the onset of stall." International Journal of Aeroacoustics 16, no. 3 (April 2017): 181–95. http://dx.doi.org/10.1177/1475472x17709929.

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The aerodynamic noise of a NACA 0012 and NACA 0021 aerofoil is measured and compared in order to determine whether there are differences in their noise signatures with a focus on the onset of stall. Measurements of the self-noise of each aerofoil are measured in an open-jet Anechoic Wind Tunnel at Reynolds numbers of 64,000 and 96,000, at geometric angles of attack from −5° through 40° at a resolution of 1°. Further measurements are taken at Re = 96,000 at geometric angles of attack from −5 through 16° at a resolution of 0.5°. Results show that while the noise generated far into the stall regime is quite similar for both aerofoils the change in noise level at the onset of stall is significantly different between the two aerofoils with the NACA 0021 exhibiting a much sharper increase in noise levels below a chord-based Strouhal number of Stc = 1.1. This behaviour is consistent with the changes in lift of these aerofoils as well as the rate of collapse of the suction peak of a NACA 0012 aerofoil under these flow conditions.

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Chaitanya, P., P. Joseph, S. Narayanan, C. Vanderwel, J. Turner, J. W. Kim, and B. Ganapathisubramani. "Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence–aerofoil interaction noise." Journal of Fluid Mechanics 818 (April 4, 2017): 435–64. http://dx.doi.org/10.1017/jfm.2017.141.

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This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto three-dimensional aerofoils. The influence on the noise reduction of the turbulence integral length scale is also studied. An optimum serration wavelength is identified whereby maximum noise reductions are obtained, corresponding to when the transverse integral length scale is approximately one-fourth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number $St_{h}=fh/U$, where $f$, $h$ and $U$ are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil self-noise dominates the interaction noise. Leading edge serrations are also shown to reduce aerofoil self-noise. The mechanism for this phenomenon is explored through particle image velocimetry measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.

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Ayton, Lorna J., and Paruchuri Chaitanya. "Analytical and experimental investigation into the effects of leading-edge radius on gust–aerofoil interaction noise." Journal of Fluid Mechanics 829 (September 26, 2017): 780–808. http://dx.doi.org/10.1017/jfm.2017.594.

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This paper investigates the effects of local leading-edge geometry on unsteady aerofoil interaction noise. Analytical results are obtained by extending previous work for parabolic leading edges to leading edges of the form $x^{m}$ for $0<m<1$. Rapid distortion theory governs the interaction of an unsteady vortical perturbation with a rigid aerofoil in compressible steady mean flow that is uniform far upstream. For high-frequency gusts interacting with aerofoils of small total thickness this allows a matched asymptotic solution to be obtained. This paper mainly focusses on obtaining the analytic solution in the leading-edge inner region, which is the dominant term in determining the total far-field acoustic directivity, and contains the effects of the local leading-edge geometry. Experimental measurements for the noise generated by aerofoils with different leading-edge nose radii in uniform flow with approximate homogeneous, isotropic turbulence are also presented. Both experimental and analytic results predict that a larger nose radius generates less overall noise in low-Mach-number flow. By considering individual terms in the analytic solution, this paper is able to propose reasons behind this result.

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NASH, EMMA C., MARTIN V. LOWSON, and ALAN McALPINE. "Boundary-layer instability noise on aerofoils." Journal of Fluid Mechanics 382 (March 10, 1999): 27–61. http://dx.doi.org/10.1017/s002211209800367x.

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An experimental and theoretical investigation has been carried out to understand the tonal noise generation mechanism on aerofoils at moderate Reynolds number. Experiments were conducted on a NACA0012 aerofoil section in a low-turbulence closed working section wind tunnel. Narrow band acoustic tones were observed up to 40 dB above background noise. The ladder structure of these tones was eliminated by modifying the tunnel to approximate to anechoic conditions. High-resolution flow velocity measurements have been made with a three-component laser-Doppler anemometer (LDA) which have revealed the presence of strongly amplified boundary-layer instabilities in a region of separated shear flow just upstream of the pressure surface trailing edge, which match the frequency of the acoustic tones. Flow visualization experiments have shown these instabilities to roll up to form a regular Kármán-type vortex street.A new mechanism for tonal noise generation has been proposed, based on the growth of Tollmien–Schlichting (T–S) instability waves strongly amplified by inflectional profiles in the separating laminar shear layer on the pressure surface of the aerofoil. The growth of fixed frequency, spatially growing boundary-layer instability waves propagating over the aerofoil pressure surface has been calculated using experimentally obtained boundary-layer characteristics. The effect of boundary-layer separation has been incorporated into the model. Frequency selection and prediction of T–S waves are in remarkably good agreement with experimental data.

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Ayton, Lorna J., and N. Peake. "On high-frequency noise scattering by aerofoils in flow." Journal of Fluid Mechanics 734 (October 8, 2013): 144–82. http://dx.doi.org/10.1017/jfm.2013.477.

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AbstractA theoretical model is developed for the sound scattered when a sound wave is incident on a cambered aerofoil at non-zero angle of attack. The model is based on the linearization of the Euler equations about a steady subsonic flow, and is an adaptation of previous work which considered incident vortical disturbances. Only high-frequency sound waves are considered. The aerofoil thickness, camber and angle of attack are restricted such that the steady flow past the aerofoil is a small perturbation to a uniform flow. The singular perturbation analysis identifies asymptotic regions around the aerofoil; local ‘inner’ regions, which scale on the incident wavelength, at the leading and trailing edges of the aerofoil; Fresnel regions emanating from the leading and trailing edges of the aerofoil due to the coalescence of singularities and points of stationary phase; a wake transition region downstream of the aerofoil leading and trailing edge; and an outer region far from the aerofoil and wake. An acoustic boundary layer on the aerofoil surface and within the transition region accounts for the effects of curvature. The final result is a uniformly-valid solution for the far-field sound; the effects of angle of attack, camber and thickness are investigated.

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Yakhina, Gyuzel, Michel Roger, Stéphane Moreau, Lap Nguyen, and Vladimir Golubev. "Experimental and Analytical Investigation of the Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Aerofoils." Acoustics 2, no. 2 (May 14, 2020): 293–329. http://dx.doi.org/10.3390/acoustics2020018.

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An experimental and analytical study of the tonal trailing-edge noise of a symmetric NACA-0012 aerofoil and of a cambered SD7003 aerofoil has been achieved. It provides a complete experimental database for both aerofoils and improves the understanding of the underlying mechanisms. The analysis stresses the high sensitivity of the tonal noise phenomenon to the flow velocity and the angle of attack. Several regimes of the noise emission are observed depending on the aforementioned parameters. The contributions of the pressure and the suction sides are found to vary with the flow parameters too. A special attention has been paid to the role of the separation bubble in the tonal noise generation. Hot-wire measurements and flow visualization prove that the separation bubble is a necessary condition for the tonal noise production. Moreover, the bubble must be located close enough to the trailing edge. Several tests with small-scale upstream turbulence confirm the existence of the feedback loop. Analytical predictions with a classical trailing-edge noise model show a good agreement with the experimental data; they confirm the cause-to-effect relationship between the wall-pressure fluctuations and the radiated sound. Finally, previously reported works on fans and propellers are shortly re-addressed to show that the tonal noise associated with laminar-boundary-layer instabilities can take place in rotating blade technology.

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Hajian, Rozhin, and Justin W. Jaworski. "The steady aerodynamics of aerofoils with porosity gradients." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2205 (September 2017): 20170266. http://dx.doi.org/10.1098/rspa.2017.0266.

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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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Chaitanya, P., P. Joseph, S. Narayanan, and J. W. Kim. "Aerofoil broadband noise reductions through double-wavelength leading-edge serrations: a new control concept." Journal of Fluid Mechanics 855 (September 14, 2018): 131–51. http://dx.doi.org/10.1017/jfm.2018.620.

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Aerofoils operating in a turbulent flow generate broadband noise by scattering vorticity into sound at the leading edge. Previous work has demonstrated the effectiveness by which serrations, or undulations, introduced onto the leading edge, can substantially reduce broadband leading-edge noise. All of this work has focused on sinusoidal (single-wavelength) leading-edge serration profiles. In this paper, a new leading-edge serration geometry is proposed which provides significantly greater noise reductions compared to the maximum noise reductions achievable by single-wavelength serrations of the same amplitude. This is achieved through destructive interference between different parts of the aerofoil leading edge, and therefore involves a fundamentally different noise reduction mechanism from conventional single-wavelength serrations. The new leading-edge serration profiles simply comprise the superposition of two single-wavelength components of different wavelength, amplitude and phase with the objective of forming two roots that are sufficiently close together and separated in the streamwise direction. Compact sources located at these root locations then interfere, leading to less efficient radiation than single-wavelength geometries. A detailed parametric study is performed experimentally to investigate the sensitivity of the noise reductions to the profile geometry. A simple model is proposed to explain the noise reduction mechanism for these double-wavelength serration profiles and shown to be in close agreement with the measured noise reduction spectra. The study is primarily performed on flat plates in an idealized turbulent flow. The paper concludes by introducing the double-wavelength serration on a 10 % thick aerofoil, where near-identical noise reductions are obtained compared to the flat plate.

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SATO, Yukiko, and Hideki ONODERA. "Reduction of aerodynamic noise from windturbine aerofoil." Proceedings of Autumn Conference of Tohoku Branch 2003.39 (2003): 139–40. http://dx.doi.org/10.1299/jsmetohoku.2003.39.139.

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Pröbsting, S., J. Serpieri, and F. Scarano. "Experimental investigation of aerofoil tonal noise generation." Journal of Fluid Mechanics 747 (April 23, 2014): 656–87. http://dx.doi.org/10.1017/jfm.2014.156.

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AbstractThe present study investigates the mechanisms associated with tonal noise emission from a NACA 0012 aerofoil at moderate incidence ($0^{\circ },1^{\circ },2^{\circ }$ and $4^{\circ }$ 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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Ayton, Lorna J. "Bioinspired aerofoil adaptations: the next steps for theoretical models." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2159 (October 14, 2019): 20190070. http://dx.doi.org/10.1098/rsta.2019.0070.

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The extended introduction in this paper reviews the theoretical modelling of leading- and trailing-edge noise, various bioinspired aerofoil adaptations to both the leading and trailing edges of blades, and how these adaptations aid in the reduction of aerofoil–turbulence interaction noise. Attention is given to the agreement between current theoretical predictions and experimental measurements, in particular, for turbulent interactions at the trailing edge of an aerofoil. Where there is a poor agreement between theoretical models and experimental data the features neglected from the theoretical models are discussed. Notably, it is known that theoretical predictions for porous trailing-edge adaptations do not agree well with experimental measurements. Previous works propose the reason for this: theoretical models do not account for surface roughness due to the porous material and thus omit a key noise source. The remainder of this paper, therefore, presents an analytical model, based upon the acoustic analogy, to predict the far-field noise due to a rough surface at the trailing edge of an aerofoil. Unlike previous roughness noise models which focus on roughness over an infinite wall, the model presented here includes diffraction by a sharp edge. The new results are seen to be in better agreement with experimental data than previous models which neglect diffraction by an edge. This new model could then be used to improve theoretical predictions for far-field noise generated by turbulent interactions with a (rough) porous trailing edge. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

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Biedermann, Till M., Pasquale Czeckay, Nils Hintzen, Frank Kameier, and C. O. Paschereit. "Applicability of Aeroacoustic Scaling Laws of Leading Edge Serrations for Rotating Applications." Acoustics 2, no. 3 (July 23, 2020): 579–94. http://dx.doi.org/10.3390/acoustics2030030.

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The dominant aeroacoustic mechanisms of serrated leading edges, subjected to highly turbulent inflow conditions, can be compressed to spanwise decorrelation effects as well as effects of destructive interference. For single aerofoils, the resulting broadband noise reduction is known to follow spectral scaling laws. However, transferring serrated leading edges to rotating machinery, results in noise radiation patterns of significantly increased complexity, impeding to allocate the observed noise reduction to the underlying physical mechanisms. The current study aims at concatenating the scaling laws for stationary aerofoil and rotating-blade application and thus at providing valuable information on the aeroacoustic transferability of leading edge serrations. For the pursued approach, low-pressure axial fans are designed, obtaining identical serrated fan blade geometries than previously analyzed single aerofoils, hence allowing for direct comparison. Highly similar spectral noise reduction patterns are obtained for the broadband noise reduction of the serrated rotors, generally confirming the transferability and showing a scaling with the geometrical parameters of the serrations as well as the inflow conditions. Continuative analysis of the total noise reduction, however, constrains the applicability of the scaling laws to a specific operating range of the rotors and motivates for a devaluation of the scaling coefficients regarding additional rotor-specific effects.

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Tam, Christopher K. W., and Hongbin Ju. "Aerofoil tones at moderate Reynolds number." Journal of Fluid Mechanics 690 (December 1, 2011): 536–70. http://dx.doi.org/10.1017/jfm.2011.465.

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AbstractIt is known experimentally that an aerofoil immersed in a uniform stream at a moderate Reynolds number emits tones. However, there have been major differences in the experimental observations in the past. Some experiments reported the observation of multiple tones, with strong evidence that these tones are most probably generated by a feedback loop. There is also an experiment reporting the observation of a single tone with no tonal jump or other features associated with feedback. In spite of the obvious differences in the experimental observations published in the literature, it is noted that all the dominant tone frequencies measured in all the investigations are in agreement with an empirically derived Paterson formula. The objective of the present study is to perform a direct numerical simulation (DNS) of the flow and acoustic phenomenon to investigate the tone generation mechanism. When comparing with experimental studies, numerical simulations appear to have two important advantages. The first is that there is no background wind tunnel noise in numerical simulation. This avoids the signal-to-noise ratio problem inherent in wind tunnel experiments. In other words, it is possible to study tones emitted by a truly isolated aerofoil computationally. The second advantage is that DNS produces a full set of space–time data, which can be very useful in determining the tone generation processes. The present effort concentrates on the tones emitted by three NACA0012 aerofoils with a slightly rounded trailing edge but with different trailing edge thickness at zero degree angle of attack. At zero degree angle of attack, in the Reynolds number range of$2\ensuremath{\times} 1{0}^{5} $to$5\ensuremath{\times} 1{0}^{5} $, the boundary layer flow is attached nearly all the way to the trailing edge of the aerofoil. Unlike an aerofoil at an angle of attack, there is no separation bubble, no open flow separation. All the flow separation features tend to increase the complexity of the tone generation processes. The present goal is limited to finding the basic tone generation mechanism in the simplest flow configuration. Our DNS results show that, for the flow configuration under study, the aerofoil emits only a single tone. This is true for all three aerofoils over the entire Reynolds number range of the present study. In the literature, it is known that Kelvin–Helmholtz instabilities of free shear layers generally have a much higher spatial growth rate than that of the Tollmien–Schlichting boundary layer instabilities. A near-wake non-parallel flow instability analysis is performed. It is found that the tone frequencies are the same as the most amplified Kelvin–Helmholtz instability at the location where the wake has a minimum half-width. This suggests that near-wake instability is the energy source of aerofoil tones. However, flow instabilities at low subsonic Mach numbers generally do not cause strong tones. An investigation of how near-wake instability generates tones is carried out using the space–time data provided by numerical simulations. Our observations indicate that the dominant tone generation process is the interaction of the oscillatory motion of the near wake, driven by flow instability, with the trailing edge of the aerofoil. Secondary mechanisms involving unsteady near-wake motion and the formation of discrete vortices in regions further downstream are also observed.

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Kim, Jae Wook, Sina Haeri, and Phillip F. Joseph. "On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges." Journal of Fluid Mechanics 792 (March 3, 2016): 526–52. http://dx.doi.org/10.1017/jfm.2016.95.

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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 (free-stream Mach number of 0.24). Full three-dimensional 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-cutoff 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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De Gennaro, Michele, Helmut Kühnelt, and Alessandro Zanon. "Numerical Prediction of the Tonal Airborne Noise for a NACA 0012 Aerofoil at Moderate Reynolds Number Using a Transitional URANS Approach." Archives of Acoustics 42, no. 4 (December 20, 2017): 653–75. http://dx.doi.org/10.1515/aoa-2017-0069.

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Abstract Tonal airborne noise of aerofoils appears in a limited range of moderate Reynolds numbers and angles of attack. In these specific conditions, the aerofoil is characterised by a large region of laminar flow over the aerodynamic surface, typically resulting in two-dimensional laminar instabilities in the boundary layer, generating one or more acoustic tones. The numerical simulation of such phenomenon requires, beside an accurate prediction of the unsteady flow field, a proper modelling of the laminar to turbulent transition of the boundary layer, which generally imposes the use of highly CPU demanding approaches such as large eddy simulation (LES) or direct numerical simulation (DNS). This paper aims at presenting the results of numerical experiments for evaluating the capability of capturing the tonal airborne noise by using an advanced, yet low computationally demanding, unsteady Reynolds-averaged Navier-Stokes (URANS) turbulence model augmented with a transitional model to account for the laminar to turbulent transition. This approach, coupled with the Ffowcs Williams and Hawkings (FW-H) acoustic analogy, is adopted for predicting the far-field acoustic sound pressure of a NACA 0012 aerofoil with Reynolds number ranging from 0.39 · 106 to 1.09 · 106. The results show a main tone located approximately at 1.6-1.8 kHz for a Reynolds number equal to 0.62 · 106, increasing to 2.4 kHz at Reynolds number equal to 0.85 · 106 and 3.4 kHz at 1.09 · 106, while no main tones are observed at 0.39 · 106. The computed spectra confirm that the acoustic emission of the aerofoil is dominated by tonal structures and that the frequency of the main tone depends on the Reynolds number consistently with the ladder-like tonal structure suggested by Paterson et al. Moreover, in specific conditions, the acoustic spectra exhibit a multi-tonal structure visible in narrowband spectra, in line with the findings of Arbey and Bataille. The presented results demonstrate the capability of the numerical model of predicting the physics of the tonal airborne noise generation.

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ROGER, MICHEL. "On broadband jet–ring interaction noise and aerofoil turbulence-interaction noise predictions." Journal of Fluid Mechanics 653 (May 5, 2010): 337–64. http://dx.doi.org/10.1017/s0022112010000285.

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The aerodynamic noise of a thin rigid annulus (referred to as the ring here) placed in the mixing layer of a subsonic circular jet is investigated in the paper, both theoretically and experimentally. From the experimental point of view, the jet–ring configuration is understood as an axisymmetric alternative to more usual ones involving a rectangular aerofoil held between parallel side plates, dedicated to the study of the noise due to the impingement of upstream turbulence. The main advantages of the circular geometry are a minimum background noise, the absence of tip effects and more specifically the account for all radiation angles from the surface in the far-field acoustic signature. The circular set-up is well suited for the study of pure broadband interaction noise only if the flow remains free of self-sustained oscillations. This is ensured by keeping a sufficient interaction distance between the nozzle and the ring, and by shaping serrations on the nozzle lip. From the theoretical point of view, an analytical model is derived as a straightforward extension of existing formulations. The induced unsteady lift forces on the ring are first inferred from a linearized unsteady aerodynamic theory and the far field is calculated in a second step by a radiation integral. This relates the far-field acoustic pressure power spectral density (PSD) to the two-wavenumber spectrum of the radial turbulent velocity at the ring location, by means of an aeroacoustic transfer function. The latter is shown asymptotically identical to the one detailed in the Appendix for a rectangular aerofoil, in the limit of relatively high frequencies. The analytical acoustic predictions are found to agree well with the measurements over an extended frequency range, provided that the model is fed with turbulent velocity input data measured by a hot-wire probe. Indirectly, this agreement validates the transfer function for a rectangular aerofoil at oblique radiation angles, which is not achievable in a set-up involving side plates and a rectangular nozzle.

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MINORIKAWA, Gaku, Shoji SUZUKI, Shimpei MIZUKI, Hoshio TSUJITA, Hiromitsu TO, and Toshiyuki HIRANO. "703 Noise characteristics of three dimensional aerofoil fan." Proceedings of Yamanashi District Conference 2000 (2000): 209–10. http://dx.doi.org/10.1299/jsmeyamanashi.2000.209.

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Ying, Wei, Ryu Fattah, Sinforiano Cantos, Siyang Zhong, and Tatiana Kozubskaya. "Computational aeroacoustics of aerofoil leading edge noise using the volume penalization-based immersed boundary methods." International Journal of Aeroacoustics 21, no. 1-2 (March 2022): 74–94. http://dx.doi.org/10.1177/1475472x221079557.

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Broadband noise due to the turbulence-aerofoil interaction, which is also called the leading edge noise, is one of the major noise sources of aircraft (including the engine). To study the noise properties numerically is a popular approach with the increasing power of computers. Conventional approaches of using body-fitted grids at the boundaries would be convoluted due to the complex geometries, which can constrain the efficiency of parametric studies. A promising approach to tackle this issue is to use the immersed boundary method (IBM). Among various IBM variants, the volume penalization (VP) approach employs a masking function to identify the immersed solid boundary, and continuous forcing terms are added to the original flow governing equations to account for the boundary conditions. It is, therefore, efficient and easy to implement into the existing computational aeroacoustics solvers. In this work, the VP-based IBM is used to simulate the leading edge noise by combining with the advanced synthetic turbulence method. The simulations are conducted for both the isolated aerofoils and cascade, and the results are compared with the well-validated body-fitted grid solutions. The viscosity effect is also highlighted by comparing the results obtained by solving both Euler and Navier–Stokes equations.

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Fosas de Pando, Miguel, Peter J. Schmid, and Denis Sipp. "On the receptivity of aerofoil tonal noise: an adjoint analysis." Journal of Fluid Mechanics 812 (January 5, 2017): 771–91. http://dx.doi.org/10.1017/jfm.2016.736.

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For moderate-to-high Reynolds numbers, aerofoils are known to produce substantial levels of acoustic radiation, known as tonal noise, which arises from a complex interplay between laminar boundary-layer instabilities, trailing-edge acoustic scattering and upstream receptivity of the boundary layers on both aerofoil surfaces. The resulting acoustic spectrum is commonly characterised by distinct equally spaced peaks encompassing the frequency range of convectively amplified instability waves in the pressure-surface boundary layer. In this work, we assess the receptivity and sensitivity of the flow by means of global stability theory and adjoint methods which are discussed in light of the spatial structure of the adjoint global modes, as well as the wavemaker region. It is found that for the frequency range corresponding to acoustic tones the direct global modes capture the growth of instability waves on the suction surface and the near wake together with acoustic radiation into the far field. Conversely, it is shown that the corresponding adjoint global modes, which capture the most receptive region in the flow to external perturbations, have compact spatial support in the pressure surface boundary layer, upstream of the separated flow region. Furthermore, we find that the relative spatial amplitude of the adjoint modes is higher for those modes whose real frequencies correspond to the acoustic peaks. Finally, analysis of the wavemaker region points at the pressure surface near 30 % of the chord as the preferred zone for the placement of actuators for flow control of tonal noise.

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Wolf, William R., João Luiz F. Azevedo, and Sanjiva K. Lele. "Convective effects and the role of quadrupole sources for aerofoil aeroacoustics." Journal of Fluid Mechanics 708 (August 10, 2012): 502–38. http://dx.doi.org/10.1017/jfm.2012.327.

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AbstractThe present investigation of aerofoil self-noise generation and propagation concerns the effects of mean flow and quadrupole sources on the broadband noise that arises from the interaction of turbulent boundary layers with the aerofoil trailing edge and the tonal noise that arises from vortex shedding generated by laminar boundary layers and trailing-edge bluntness. Compressible large-eddy simulations (LES) are conducted for a NACA0012 aerofoil with rounded trailing edge for four flow configurations with different angles of incidence, boundary layer tripping configurations and free-stream Mach numbers. The Reynolds number based on the aerofoil chord is fixed at ${\mathit{Re}}_{c} = 408\hspace{0.167em} 000$. The acoustic predictions are performed by the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation and incorporate convective effects. Surface and volume integrations of dipole and quadrupole source terms appearing in the FWH equation are performed using a three-dimensional wideband multi-level adaptive fast multipole method (FMM) in order to accelerate the calculations of aeroacoustic integrals. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and good agreement is observed in terms of both aerodynamic and aeroacoustic results. For low-Mach-number flows, quadrupole sources can be neglected in the FWH equation and mean flow effects appear only for high frequencies. However, for higher speeds, convection effects are relevant for all frequencies and quadrupole sources have a more pronounced effect for medium and high frequencies. The convective effects are most readily observed in the upstream direction.

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Turner, Jacob M., and Jae Wook Kim. "On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction." Journal of Fluid Mechanics 871 (May 17, 2019): 186–211. http://dx.doi.org/10.1017/jfm.2019.314.

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Existing studies suggest that wavy leading edges (WLEs) offer substantial reduction of broadband noise generated by an aerofoil undergoing upstream vortical disturbances. In this context, there are two universal trends in the frequency spectra of the noise reduction which have been observed and reported to date: (i) no significant reduction at low frequencies followed by (ii) a rapid growth of the noise reduction that persists in the medium-to-high frequency range. These trends are known to be insensitive to the aerofoil type and flow condition used. This paper aims to provide comprehensive understandings as to how these universal trends are formed and what the major drivers are. The current work is based on very-high-resolution numerical simulations of a semi-infinite flat-plate aerofoil impinged by a prescribed divergence-free vortex in an inviscid base flow at zero incidence angle, continued from recent work by the authors (Turner & Kim, J. Fluid Mech., vol. 811, 2017, pp. 582–611). One of the most significant findings in the current work is that the noise source distribution on the aerofoil surface becomes entirely two-dimensional (highly non-uniform in the spanwise direction as well as streamwise) at high frequencies when the WLE is involved. Also, the sources downstream of the LE make crucial contributions to creating the universal trends across all frequencies. These findings contradict the conventional LE-focused one-dimensional source analysis that has widely been accepted for all frequencies. The current study suggests that the universal trends in the noise-reduction spectra can be properly understood by taking the downstream source contributions into account, in terms of both magnitude and phase variations. After including the downstream sources, it is shown in this paper that the first universal trend is due to the conservation of total (surface integrated) source energy at low frequencies. The surface-integrated source magnitude that decreases faster with the WLE correlates very well with the noise-reduction spectrum at medium frequencies. In the meantime, the high-frequency noise reduction is driven almost entirely by destructive phase interference that increases rapidly and consistently with frequency, explaining the second universal trend.

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Wu, Hao, Richard D. Sandberg, and Stéphane Moreau. "Stability characteristics of different aerofoil flows at Rec=150,000 and the implications for aerofoil self-noise." Journal of Sound and Vibration 506 (August 2021): 116152. http://dx.doi.org/10.1016/j.jsv.2021.116152.

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Kingan, Michael J., and John R. Pearse. "Laminar boundary layer instability noise produced by an aerofoil." Journal of Sound and Vibration 322, no. 4-5 (May 2009): 808–28. http://dx.doi.org/10.1016/j.jsv.2008.11.043.

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JONES, L. E., R. D. SANDBERG, and N. D. SANDHAM. "Stability and receptivity characteristics of a laminar separation bubble on an aerofoil." Journal of Fluid Mechanics 648 (April 7, 2010): 257–96. http://dx.doi.org/10.1017/s0022112009993089.

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Stability characteristics of aerofoil flows are investigated by linear stability analysis of time-averaged velocity profiles and by direct numerical simulations with time-dependent forcing terms. First the wake behind an aerofoil is investigated, illustrating the feasibility of detecting absolute instability using these methods. The time-averaged flow around an NACA-0012 aerofoil at incidence is then investigated in terms of its response to very low-amplitude hydrodynamic and acoustic perturbations. Flow fields obtained from both two- and three-dimensional simulations are investigated, for which the aerofoil flow exhibits a laminar separation bubble. Convective stability characteristics are documented, and the separation bubble is found to exhibit no absolute instability in the classical sense; i.e. no growing disturbances with zero group velocity are observed. The flow is however found to be globally unstable via an acoustic-feedback loop involving the aerofoil trailing edge as a source of acoustic excitation and the aerofoil leading-edge region as a site of receptivity. Evidence suggests that the feedback loop may play an important role in frequency selection of the vortex shedding that occurs in two dimensions. Further simulations are presented to investigate the receptivity process by which acoustic waves generate hydrodynamic instabilities within the aerofoil boundary layer. The dependency of the receptivity process to both frequency and source location is quantified. It is found that the amplitude of trailing-edge noise in the fully developed simulation is sufficient to promote transition via leading-edge receptivity.

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Chaitanya, Paruchuri, Phillip Joseph, Tze Pei Chong, Matthew Priddin, and Lorna Ayton. "On the noise reduction mechanisms of porous aerofoil leading edges." Journal of Sound and Vibration 485 (October 2020): 115574. http://dx.doi.org/10.1016/j.jsv.2020.115574.

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ASAI, Motohiro, Akira URITA, and Shuji TANAKA. "731 Generation Mechanism of Discrete Frequency Noise from an Aerofoil." Proceedings of Conference of Tokai Branch 2006.55 (2006): 325–26. http://dx.doi.org/10.1299/jsmetokai.2006.55.325.

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Lau, Alex Siu Hong, Jae Wook Kim, Jeremy Hurault, Tomas Vronsky, and Phillip Joseph. "Aerofoil trailing-edge noise prediction models for wind turbine applications." Wind Energy 20, no. 10 (May 19, 2017): 1727–52. http://dx.doi.org/10.1002/we.2119.

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Jones, L. E., and R. D. Sandberg. "Acoustic and hydrodynamic analysis of the flow around an aerofoil with trailing-edge serrations." Journal of Fluid Mechanics 706 (July 6, 2012): 295–322. http://dx.doi.org/10.1017/jfm.2012.254.

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AbstractDirect numerical simulations of the flow around a NACA-0012 aerofoil are conducted, employing an immersed boundary method to represent flat-plate trailing-edge extensions both with and without serrations. Properties of the turbulent boundary layer convecting over the trailing edge are similar for both cases. For cases with serrations, the trailing-edge noise produced by the flow over the aerofoil is observed to decrease in amplitude, and the frequency interval over which the noise reduction occurs differs depending on the serration length. The directivity and spanwise coherence of the trailing-edge noise appears largely unaffected by the serrations. The hydrodynamic behaviour in the vicinity of the trailing-edge extensions is investigated. The streamwise discontinuity imparted upon the turbulent flow by the straight trailing edge can clearly be observed in statistical quantities, whereas for the serrated case no spanwise homogeneous discontinuities are observed. The trailing-edge serrations appear to break up the larger turbulent structures convecting into the wake, and to promote the development of horseshoe vortices originating at the serrations themselves.

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Al-Okbi, Yasir, Tze Pei Chong, and Oksana Stalnov. "Leading Edge Blowing to Mimic and Enhance the Serration Effects for Aerofoil." Applied Sciences 11, no. 6 (March 15, 2021): 2593. http://dx.doi.org/10.3390/app11062593.

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Leading edge serration is now a well-established and effective passive control device for the reduction of turbulence–leading edge interaction noise, and for the suppression of boundary layer separation at high angle of attack. It is envisaged that leading edge blowing could produce the same mechanisms as those produced by a serrated leading edge to enhance the aeroacoustics and aerodynamic performances of aerofoil. Aeroacoustically, injection of mass airflow from the leading edge (against the incoming turbulent flow) can be an effective mechanism to decrease the turbulence intensity, and/or alter the stagnation point. According to classical theory on the aerofoil leading edge noise, there is a potential for the leading edge blowing to reduce the level of turbulence–leading edge interaction noise radiation. Aerodynamically, after the mixing between the injected air and the incoming flow, a shear instability is likely to be triggered owing to the different flow directions. The resulting vortical flow will then propagate along the main flow direction across the aerofoil surface. These vortical flows generated indirectly owing to the leading edge blowing could also be effective to mitigate boundary layer separation at high angle of attack. The objectives of this paper are to validate these hypotheses, and combine the serration and blowing together on the leading edge to harvest further improvement on the aeroacoustics and aerodynamic performances. Results presented in this paper strongly indicate that leading edge blowing, which is an active flow control method, can indeed mimic and even enhance the bio-inspired leading edge serration effectively.

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Al-Shabab, A. A. Sheikh, and P. G. Tucker. "RANS prediction of open jet aerofoil interaction and design metrics." Aeronautical Journal 123, no. 1266 (July 24, 2019): 1275–96. http://dx.doi.org/10.1017/aer.2019.55.

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ABSTRACTRANS models remain an attractive turbulence simulation method which could provide some open jet aerofoil interaction analysis at a fraction of the cost of a high-fidelity LES approach. The present work explores the potential and limitations of RANS in this context by simulating an open jet aerofoil noise experiment using the aerospace oriented Menter SST RANS model. This model’s tendency to transition at a critical Reynolds number lower than the experimental value was found to impact the boundary layer development. However, the introduction of a low-Re correction improved the prediction of surface pressure and skin friction, enabling the suction surface separation bubble to be captured. The free shear layer’s virtual origin characteristics exhibited sensitivity to the interaction with the aerofoil, which can be developed into a metric of the interaction. The main challenge for RANS was accounting for the rise in background disturbance level in the working section, which is caused by the high-turbulence intensity in the free shear layers.

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Nakano, Tomonori, and Nobuyuki Fujisawa. "Simultaneous measurement of noise and velocity field under discrete tone noise from a symmetrical aerofoil." Journal of the Visualization Society of Japan 24, Supplement1 (2004): 337–40. http://dx.doi.org/10.3154/jvs.24.supplement1_337.

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Lau, Alex S. H., Sina Haeri, and Jae Wook Kim. "The effect of wavy leading edges on aerofoil–gust interaction noise." Journal of Sound and Vibration 332, no. 24 (November 2013): 6234–53. http://dx.doi.org/10.1016/j.jsv.2013.06.031.

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Chen, Weijie, Weiyang Qiao, Fan Tong, Liangfeng Wang, and Xunnian Wang. "Experimental investigation of wavy leading edges on rod-aerofoil interaction noise." Journal of Sound and Vibration 422 (May 2018): 409–31. http://dx.doi.org/10.1016/j.jsv.2018.02.043.

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34

Rama Krishna, S., A. Rama Krishna, and K. Ramji. "An experimental study on the reduction of motor-fan noise by modification of the blade and shroud configuration." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 2 (February 1, 2010): 315–20. http://dx.doi.org/10.1243/09544062jmes1869.

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The noise reduction (NR) of fans used for cooling electric motors is one of the key parameters in the design of a motor fan. In the authors’ previous paper, aeroacoustic analysis (which is based on unsteady computational fluid dynamics results) was performed for the baseline fan to know its sound level. To further find a better blade shape from an NR point of view, aeroacoustic analysis on various blade profiles from the NACA-63 and NACA-65 series was conducted. In this work, an experimental study on the baseline fan and three redesigned composite material fans for the low-noise fan is performed. The experimental parameters under investigation are better aerofoil-shape blade cross-section, using inlet bell-mouth entry, using composite materials, reducing the number of blades, using uneven blade spacing, making it a mixed flow fan, using backward-skewed blade design and reducing tip clearance. From the noise measurements in a semi-anechoic chamber for Fan-2, it is observed that the overall NR was 12.8 dB(A) compared with the baseline fan. It is observed that a mixed flow fan consisting of seven evenly spaced blades of NACA 65-010 aerofoil cross-section with backward swept shape and fabricated with glass and jute fibre produced the low-noise fan design at the fan operating point.

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Chaitanya, P., and P. Joseph. "Slitted leading edge profiles for the reduction of turbulence-aerofoil interaction noise." Journal of the Acoustical Society of America 143, no. 6 (June 2018): 3494–504. http://dx.doi.org/10.1121/1.5040972.

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Lacagnina, Giovanni, Paruchuri Chaitanya, Jung-Hoon Kim, Tim Berk, Phillip Joseph, Kwing-So Choi, Bharathram Ganapathisubramani, et al. "Leading edge serrations for the reduction of aerofoil self-noise at low angle of attack, pre-stall and post-stall conditions." International Journal of Aeroacoustics 20, no. 1-2 (February 1, 2021): 130–56. http://dx.doi.org/10.1177/1475472x20978379.

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This paper addresses the usefulness of leading edge serrations for reducing aerofoil self-noise over a wide range of angles of attack. Different serration geometries are studied over a range of Reynolds number [Formula: see text]. Design guidelines are proposed that permit noise reductions over most angles of attack. It is shown that serration geometries reduces the noise but adversely effect the aerodynamic performance suggesting that a trade-off should be sought between these two considerations. The self-noise performance of leading edge serrations has been shown to fall into three angle of attack (AoA) regimes: low angles where the flow is mostly attached, moderate angles where the flow is partially to fully separated, and high angles of attack where the flow is fully separated. Leading edge serrations have been demonstrated to be effective in reducing noise at low and high angles of attack but ineffective at moderate angles. The noise reduction mechanisms are explored in each of three angle regimes.

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Liu, Pei Qing, Yan Xiang Cui, Liang Wang, and Qiu Lin Qu. "Computational Investigation of the Slat Blowing Control for High-Lift Airfoil." Applied Mechanics and Materials 138-139 (November 2011): 223–28. http://dx.doi.org/10.4028/www.scientific.net/amm.138-139.223.

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Based on the characteristics of blowing control, a new technique was put forward to weaken slat cove separation and reduce noise. The effect of the slat blowing control on lift performance, the flow field and noise with a three-element high lift aerofoil was investigated by using the computational fluid dynamics (CFD) code of Fluent and the Reynolds-averaged Navier-Stokes equations. The blowing apertures were set on the lower surface of the slat. By using the slat blowing technique, the slat cove separation can be controlled efficiently and the lift coefficient increased. The aerodynamic performance varies with different blowing flow rates and angles of attack.

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38

TAKAGI, Yuichi, Nobuyuki FUJISAWA, and Tomonori NAKANO. "Reduction mechanism of discrete frequency noise from a symmetrical aerofoil by cylinder wake." Journal of the Visualization Society of Japan 23, Supplement2 (2003): 83–86. http://dx.doi.org/10.3154/jvs.23.supplement2_83.

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39

Wu, Hao, Stéphane Moreau, and Richard D. Sandberg. "On the noise generated by a controlled-diffusion aerofoil at Rec=1.5×105." Journal of Sound and Vibration 487 (November 2020): 115620. http://dx.doi.org/10.1016/j.jsv.2020.115620.

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40

Kim, Jae Wook, and Sina Haeri. "An advanced synthetic eddy method for the computation of aerofoil–turbulence interaction noise." Journal of Computational Physics 287 (April 2015): 1–17. http://dx.doi.org/10.1016/j.jcp.2015.01.039.

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41

Watkins, Joseph, and Abdessalem Bouferrouk. "The Effects of a Morphed Trailing-Edge Flap on the Aeroacoustic and Aerodynamic Performance of a 30P30N Aerofoil." Acoustics 4, no. 1 (March 3, 2022): 248–67. http://dx.doi.org/10.3390/acoustics4010015.

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This paper presents initial results on the aeroacoustic and aerodynamic effects of morphing the trailing-edge flap of the 30P30N aerofoil, over five flap deflections (5–25°), at an 8° angle of attack and a Reynolds number of Re=9.2×105. The Ffowcs-Williams–Hawkings acoustic analogy estimates the far-field noise, whilst the flow field is solved using URANS with the four-equation Transition SST model. Aerodynamic and aeroacoustic simulation data for the 30P30N’s full configuration compare well with experimental results. A Courant number (C) ≤ 1 should be used for resolving tonal noise, whilst a C of up to 4 is sufficient for broadband noise. Sound pressure level results show an average 11% reduction in broadband noise across all flap deflections and frequencies for the morphed configuration compared with the conventional, single-slotted flap. The morphed flap eliminates the multiple tonal peaks observed in the conventional design. Beyond 15° flap deflection, the morphing flap achieves higher stall angles, but with increased drag, leading to a maximum reduction of 17% in Cl/Cd ratio compared with the conventional flap. The methodology reported here for the 30P30N is a quick tool for initial estimates of the far-field noise and aerodynamic performance of a morphing flap at the design stage.

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42

Zhang, Minghui, and Tze Pei Chong. "Effects of porous trailing edge on aerodynamic noise characteristics." International Journal of Aeroacoustics 19, no. 3-5 (June 2020): 254–71. http://dx.doi.org/10.1177/1475472x20937941.

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The objective of this work is to investigate the effect of the porous trailing edge on the aeroacoustics performance of the NACA 65(12)-10 aerofoil. The motivation behind this study is to investigate the effect of the porous parameters to explore the noise control concepts. Experimental testing in an aeroacoustics open jet wind tunnel was performed at chord-based Reynolds numbers between 0.2 and 0.6 million, and effective angles of attack at ±1.7 degree, including at 0 degrees. The porous trailing edge at porosity 30% with different holes diameters and the length of these porous trailing edges are used in the acoustic experiments. The study reveals that the level of the reduction of the broadband noise becomes larger as the diameter of the holes decreases and the length of the porous trailing edge increases at lower Reynolds numbers. Bluntness-induced tone noise is produced at high Reynolds number. Meanwhile, the porous trailing edge can suppress the laminar instability noise at the middle and low frequency regions.

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43

Ayton, Lorna J., and Paruchuri Chaitanya. "An analytical and experimental investigation of aerofoil–turbulence interaction noise for plates with spanwise-varying leading edges." Journal of Fluid Mechanics 865 (February 18, 2019): 137–68. http://dx.doi.org/10.1017/jfm.2019.78.

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This paper presents an analytic solution for gust–aerofoil interaction noise for flat plates with spanwise-varying periodic leading edges in uniform mean flow. The solution is obtained by solving the linear inviscid equations via separation of variables and the Wiener–Hopf technique, and is suitable for calculating the far-field noise generated by any leading edge with a single-valued piecewise linear periodic spanwise geometry. Acoustic results for homogeneous isotropic turbulent flow are calculated by integrating the single-gust solution over a wavenumber spectrum. The far-sound pressure level is calculated for five test-case geometries; sawtooth serration, slitted $v$-root, slitted $u$-root, chopped peak and square wave, and compared to experimental measurements. Good agreement is seen over a range of frequencies and tip-to-root ratios (varying the sharpness of the serration). The analytic solution is then used to calculate the propagating pressure along the leading edge of the serration for fixed spanwise wavenumbers, i.e. only the contribution to the surface pressure which propagates to the far field. Using these results, two primary mechanisms for noise reduction are discussed; tip and root interference, and a redistribution of energy from cuton modes to cutoff modes. A secondary noise-reduction mechanism due to nonlinear features is also discussed and seen to be particularly important for leading edges with very narrow slits.

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44

Fosas de Pando, Miguel, Peter J. Schmid, and Denis Sipp. "A global analysis of tonal noise in flows around aerofoils." Journal of Fluid Mechanics 754 (July 30, 2014): 5–38. http://dx.doi.org/10.1017/jfm.2014.356.

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AbstractThe generation of discrete acoustic tones in the compressible flow around an aerofoil is addressed in this work by means of nonlinear numerical simulations and global stability analyses. The nonlinear simulations confirm the appearance of discrete tones in the acoustic spectrum and, for the chosen flow case, the global stability analyses of the mean-flow dynamics reveal that the linearized operator is stable. However, the flow response to incoming disturbances exhibits important transient growth effects that culminate in the onset of aeroacoustic feedback loops, involving instability processes on the suction- and pressure-surface boundary layers together with their cross-interaction by acoustic radiation at the trailing edge. The features of the aeroacoustic feedback loops and the appearance of discrete tones are then related to the features of the least-stable modes in the global spectrum: the spatial structure of the direct modes displays the coupled dynamics of hydrodynamic instabilities on the suction surface and in the near wake. Finally, different families of global modes will be identified and the dynamics that they represent will be discussed.

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Lin, Y., R. Vadlamani, M. Savill, and P. Tucker. "Wall-resolved large eddy simulation for aeroengine aeroacoustic investigation." Aeronautical Journal 121, no. 1242 (June 22, 2017): 1032–50. http://dx.doi.org/10.1017/aer.2017.54.

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ABSTRACTThe work presented here forms part of a larger project on Large-Eddy Simulation (LES) of aeroengine aeroacoustic interactions. In this paper, we concentrate on LES of near-field flow over an isolated NACA0012 aerofoil at zero angle-of-attack and a chord based Reynolds number ofRec= 2 × 105. A wall-resolved compressible Numerical Large Eddy Simulation (NLES) approach is employed to resolve streak-like structures in the near-wall flow regions. The calculated unsteady pressure/velocity field will be imported into an analyticallybased scheme for far-field trailing-edge noise prediction later. The boundary-layer mean and root-mean-square (rms) velocity profiles, the surface pressure fluctuation over the aerofoil, and the wake flow development are compared with experimental data and previous computational simulations in our research group. It is found that the results from the wall-resolved compressible NLES are very encouraging as they correlate well with test data. The main features of the wall-resolved compressible NLES, as well as the advantages of such compressible NLES over previous incompressible LES performed in our research group, are also discussed.

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SUZUKI, Yasumasa, Noriaki KOBAYASHI, Katsuyuki YAMAMOTO, Syunsuke MAKIMURA, Keita NISHIMURA, Yuta YOSHIZAWA, Atushi OKABE, Katsuhiko NISHIMURA, Tsuneo SUZUKI, and Chisachi KATO. "1114 Study on aerofoil noise with inflow turbulence by using the active turbulence generator." Proceedings of the Fluids engineering conference 2014 (2014): _1114–1_—_1114–4_. http://dx.doi.org/10.1299/jsmefed.2014._1114-1_.

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Turner, Jacob M., and Jae Wook Kim. "Trailing-edge noise generation from a flat-plate aerofoil interacting with a prescribed vortex." Journal of Sound and Vibration 489 (December 2020): 115654. http://dx.doi.org/10.1016/j.jsv.2020.115654.

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Turner, Jacob M., and Jae Wook Kim. "Aerofoil dipole noise due to flow separation and stall at a low Reynolds number." International Journal of Heat and Fluid Flow 86 (December 2020): 108715. http://dx.doi.org/10.1016/j.ijheatfluidflow.2020.108715.

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49

Shen, Xiang, Eldad Avital, Qinghe Zhao, Junhui Gao, Xiaodong Li, Gordon Paul, and Theodosios Korakianitis. "Surface curvature effects on the tonal noise performance of a low Reynolds number aerofoil." Applied Acoustics 125 (October 2017): 34–40. http://dx.doi.org/10.1016/j.apacoust.2017.04.002.

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50

Lau, Alex Siu Hong, Jae Wook Kim, Jeremy Hurault, and Tomas Vronsky. "A study on the prediction of aerofoil trailing-edge noise for wind-turbine applications." Wind Energy 20, no. 2 (July 25, 2016): 233–52. http://dx.doi.org/10.1002/we.2003.

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Journal articles on the topic 'Aerofoil Noise'

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