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Academic literature on the topic 'Aerofoil Noise'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "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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Dissertations / Theses on the topic "Aerofoil Noise"

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Kingan, Michael Joseph. "Aeroacoustic noise produced by an aerofoil." Thesis, University of Canterbury. Mechanical Engineering, 2005. http://hdl.handle.net/10092/6596.

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This thesis describes an investigation into the aeroacoustic noise produced by an aerofoil using experimental, computational and theoretical methods. Several different types of aeroacoustic noise generation mechanisms and the parameters which affect these mechanisms were identified and investigated. The aerofoils used' in this investigation all had chord lengths of 100mm and had a maximum thickness between 18mm and 30mm. Experimental testing was undertaken in the low noise wind tunnel in the Department of Mechanical Engineering at the University of Canterbury with the aerofoils mounted at the exit of the tunnel. Airflow speeds from 10m/s to 40m/s and a range of angles of incidence were investigated. A number of modifications were made to reduce the noise and improve the operation of the wind tunnel. Different methods of measuring the aeroacoustic noise produced by an aerofoil were also investigated. The theory of aeroacoustic noise generation is described and the effect of a scattering surface on the efficiency of these aeroacoustic noise sources was investigated. A number of different mechanisms by which an aerofoil produces aeroacoustic noise were identified. These mechanisms were divided into three main categories: (1) blunt trailing edge aerofoil noise (2) sharp trailing edge aerofoil noise and (3) stalled aerofoil noise. The effect of air temperature on the production of aeroacoustic noise was also investigated. It was found that in most instances air temperature would have little effect on aeroacoustic noise generation. An extensive study of the aeroacoustic noise produced by a number of different aerofoils was undertaken. Modelling of the airflow over the aerofoils was used to determine the mechanism by which aeroacoustic noise is produced. Several different aeroacoustic noise generation mechanisms were identified. Theoretical models were also used to model the aeroacoustic noise produced by the aerofoils. Several treatments to reduce the level of aeroacoustic noise produced by an aerofoil were investigated. The treatments reduced the aeroacoustic noise produced by an aerofoil with varying degrees of success. A method for measuring the aeroacoustic noise produced by car roof racks mounted on the roof of a vehicle using a relatively small wind tunnel was established. The noise level produced by a roof rack installed 011 the roof of a vehicle measured using this technique compared favourably with measurements made on a full vehicle in a large wind tunnel. The method shows promise as a low cost method of accurately measuring the aeroacoustic noise produced by roof racks installed on a vehicle roof.
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Paruchuri, Chaitanya. "Aerofoil geometry effects on turbulence interaction noise." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/415884/.

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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.
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Ai, Qing. "Novel morphing structures for aerofoil flow and noise control purposes." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720818.

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Lau, Alex Siu Hong. "High-order computations on aerofoil-gust interaction noise and the effects of wavy leading edges." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/355961/.

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High-order accurate numerical simulations are performed to investigate the effects of wavy leading edges on aerofoil gust interaction (AGI) noise. The present study is based on periodic velocity dis-turbances predominantly in streamwise (x-) and vertical (y-) directions that are mainly responsible for the surface pressure fluctuation of an aerofoil. The perturbed velocity components of the present gust model do not vary in the spanwise (z-) direction. In general, the present results show that wavy leading edges lead to reduced AGI noise. Under the current incident gusts, it is found that the ratio of the wavy leading-edge peak-to-peak amplitude (LEA) to the longitudinal wavelength of the incident gust (λg) is the most important factor for the reduction of AGI noise. It is observed that AGI noise reduces with increasing LEA/λg, and significant noise reduction can be achieved for LEA/λg≥0.3. The present results also suggest that any two different cases with the same LEA/λg lead to a strong similarity in their profiles of noise reduction relative to the straight leading-edge case. The wavelength of wavy leading edges (LEW), however, shows minor influence on the reduction of AGI noise under the present gust profiles used. Nevertheless, the present results show that a meaningful improvement in noise reduction may be achieved when 1.06LEW/λg 61.5. In addition, it is found that the beneficial effects of wavy leading edges are maintained for various angles of attack and aerofoil thicknesses. Also, wavy leading edges remain effective in reducing AGI noise for gust profiles containing multiple frequency components. It is discovered in the current research that wavy leading edges result in in-coherent response time to the incident gust across the span, which causes a decreased level of surface pressure fluctuations, hence a reduced level of AGI noise.
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Nash, Emma Clare. "Boundary layer instability noise on aerofoils." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337698.

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Fosas, De Pando Miguel Ángel. "Tonal noise generation in flows around aerofoils : a global stability analysis." Palaiseau, Ecole polytechnique, 2012. https://theses.hal.science/tel-00816987.

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La génération de fréquences discrètes dans l'écoulement autour d'un profil d'aile est étudiée dans cette thèse au moyen de simulations numériques non-linéaires et d'études de stabilité globale. À cette fin, un code numérique mettant en œuvre une nouvelle technique pour accéder à la dynamique linéaire, directe et adjointe, a d'abord été développé et ensuite appliqué à l'écoulement autour d'un profil. Les simulations non-linéaires confirment l'apparition de fréquences discrètes dans le spectre sonore, et pour le cas considéré, l'analyse de stabilité globale de la dynamique linéaire de l'écoulement moyen montre que celle-ci est stable. Cependant, la réponse de l'écoulement à des perturbations incidentes révèle de fortes croissances transitoires amenant à l'établissement de cycles de rétroaction aéroacoustique. Ces cycles comprennent la croissance des instabilités hydrodynamiques dans les couches limites sur l'intrados et l'extrados ainsi que leurs interactions avec les radiations acoustiques du bord de fuite. Les processus associés à l'apparition des fréquences discrètes dans le spectre sonore ainsi que les cycles de rétroaction sont ensuite mis en relation avec les modes globaux les moins stables: d'un coté, la structure spatiale des modes directs montre la croissance des instabilités hydrodynamiques sur l'extrados et la zone du sillage proche du bord de fuite; d'un autre coté, les modes adjoints associés présentent l'intrados comme la zone la plus réceptive à des perturbations externes. Finalement, l'analyse de la région dite du wavemaker indique, en accord avec les expériences, le rôle fondamental de la couche limite sur l'intrados
The generation of discrete acoustic tones in the compressible flow around an aerofoil is addressed in this thesis by means of nonlinear numerical simulations and global stability analyses. To this end, a nonlinear simulation code featuring a novel technique for gaining access to the linearized direct and adjoint dynamics has been developed and applied to the flow around an aerofoil. 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 into the onset of aeroacoustic feedback loops, involving instability process 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: on the one hand, the spatial structure of the direct modes display the growth of hydrodynamic instabilities on the suction surface and the near wake; on the other hand, the associated adjoint modes display increased receptivity of the flow on the pressure surface. Finally, the analysis of the wavemaker region highlights, in agreement with previous experimental investigations, the sensitivity of the flow to the pressure-surface boundary layer
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Ferret, Bernard. "Etude expérimentale de l'intéraction entre un tourbillon isolé et un profil d'aile." Poitiers, 1988. http://www.theses.fr/1988POIT2317.

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En soufflerie subsonique, on genere un tourbillon a partir du decrochage dynamique d'un volet mis rapidement en incidence par commande numerique. Ce tourbillon unique et reproductible se detache et est convecte par l'ecoulement sur un profil naca0012. Cette maquette, montee sur une balance de portance et de trainee instationnaires est munie de prises de pression multiplexees sur un capteur par un commutateur pneumatique
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MYERS, MATTHEW RONALD. "EFFECT OF AIRFOIL MEAN LOADING ON HIGH-FREQUENCY GUST INTERACTION NOISE (AEROACOUSTICS, FAN, TURBOMACHINERY)." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184032.

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This dissertation investigates the effect of airfoil steady loading on the sound generated by the interaction of an isolated, zero-thickness airfoil with a high-frequency convected disturbance. The analysis is based on a linearization of the inviscid equations of motion about a nonuniform mean flow. The mean flow is assumed to be two-dimensional and subsonic. Throughout most of the dissertation, we assume that the Mach number is 0(1), though in one section we concentrate on the leading-edge region and study the behavior of the sound field as the Mach number tends to zero. The small parameter representing the amount of airfoil camber and incidence angle, and the large parameter representing the ratio of airfoil chord to disturbance wavelength, are utilized in a singular perturbation analysis. The analysis shows that essentially all of the sound is generated at the leading and trailing edges, in regions the size of the disturbance wavelength. The solution in the local-leading-edge region reveals several sound-generating mechanisms which do not exist for an airfoil with no mean loading. These mechanisms are not present at the trailing edge; the trailing edge is important only as a scatterer of the sound produced at the leading edge. The propagation of sound away from the airfoil edges is described by geometric acoustics, with the amplitude varying on the scale of the airfoil chord and the phase varying on the much smaller scale of the disturbance wavelength. In addition, a diffraction-type transition region exists downstream of the airfoil. Calculations of radiated acoustic power show that the sound field depends strongly on Mach number, gust characteristics, and airfoil steady loading. Small changes in these properties can produce large changes in radiated power levels. Most importantly, we find that the amount of power radiated correlates very well with the strength of the mean flow around the leading edge.
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Schumacher, Karn Lee. "Low Reynolds Number Two- and Three-Dimensional Cavity Flows and the Effect of a Cavity on Airfoil Tonal Noise." Thesis, 2020. https://hdl.handle.net/2440/135369.

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This thesis discusses the flow over rectangular and modified cavity geometries at low Reynolds number, as well as the role of a cavity in an airfoil surface in the production of airfoil tonal noise. Cavity flows can be found on many land, air and water vehicles where they can be a significant source of tonal or broadband noise. Modifying the cavity geometry is established as an effective passive control technique for cavity flow noise. The flow about, and noise produced by, two-dimensional rectangular and modified cavity cutouts in an airfoil surface (`airfoil with cavity') were studied using an anechoic wind tunnel. As L/0o increased, the coherence of shear layer vortices decreased, with an increase in the number of cavity oscillation modes found, each with lower intensity. Mean convection velocity ratio data were reported for an extended range compared to the literature, with cavity oscillation mode numbers also reported. The effect of sloping the front and rear cavity walls was investigated, with a significant change in shear layer roll-up modes found and cavity oscillation modes detected, compared to the rectangular cavity. The production of airfoil tonal noise was unexpectedly found from the `airfoil with cavity' profile. As the cavity position was varied on the airfoil surface, the airfoil tonal frequencies were found to vary. The noise was attributed to an aeroacoustic feedback loop, of a similar form to that responsible for cavity tones - the existence of this feedback loop as it pertains to airfoil tonal noise had been debated in the literature. A region of receptivity was identified near the cavity trailing edge where inflectional velocity profiles were measured. Boundary layer disturbances at the frequencies of the airfoil tones were detected downstream of this region. These disturbances were found to be amplified over a separation bubble upstream of the airfoil trailing edge. When external acoustic forcing was applied, the airfoil tonal noise frequencies were selectively reinforced - rather than the boundary layer's entire unstable frequency range responding to the external forcing in a smooth curve peaking at the most unstable Tollmien-Schlichting wave frequency. This suggested that a constructive feedback loop existed between the airfoil trailing edge and the region of receptivity near the cavity. The flow about three-dimensional cavity cutouts in a flat plate were investigated using a recirculating water tunnel. The shear layer structure about a shallow, narrow rectangular cavity flow was characterised. At low Reynolds number, `spanwise' shear layer vortices were found to have significant curvature. The lateral growth of the cavity shear layer beyond the sides of the cavity was found to be significant, with a periodic flow pattern identified adjacent to the sides of the cavity. The pattern is explained in terms of an interaction of the streamwise-orientated portions of preceding and following shear layer vortices. This finally causes the formation of a tornado-like feature on the at plate adjacent to the sides of the cavity. An asymmetric flow structure was found about a modified chevron-like cavity geometry, which was attributed to a shear layer twisting mode.
Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2020
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Books on the topic "Aerofoil Noise"

1

Brooks, Thomas F. Airfoil self-noise and prediction. Hampton, Va: Langley Research Center, 1989.

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Brooks, Thomas F. Airfoil self-noise and prediction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Brooks, Thomas F. Airfoil self-noise and prediction. Washington, D.C: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Brooks, Thomas F. Airfoil self-noise and prediction. Washington, D.C: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Brooks, Thomas F. Airfoil self-noise and prediction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Stuart, Pope D., Marcolini Michael A, and United States. National Aeronautics and Space Administration. Scientific and Technical Information Division, eds. Airfoil self-noise and prediction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Stuart, Pope D., Marcolini Michael A, and United States. National Aeronautics and Space Administration. Scientific and Technical Information Division, eds. Airfoil self-noise and prediction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Airfoil self-noise and prediction. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Book chapters on the topic "Aerofoil Noise"

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Ayton, Lorna. "Leading-Edge Stagnation-Point Noise Generated by Turbulence in Subsonic Uniform Flow." In Asymptotic Approximations for the Sound Generated by Aerofoils in Unsteady Subsonic Flows, 145–74. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-19959-7_5.

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Prasad Maddula, Satya, Vasishta Bhargava Nukala, Swamy Naidu Neigapula Venkata, Chinmaya Prasad Padhy, and Rahul Samala. "Trailing Edge Bluntness Noise Characterization for Horizontal Axis Wind Turbines [HAWT] Blades." In Acoustic Emission - New Perspectives and Applications. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.99880.

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Abstract:
Wind turbine noise is becoming a critical issue for many offshore and land-based wind projects. In this work, we analyzed trailing edge bluntness vortex shedding noise source for a land-based turbine of size 2 MW and blade span of 38 m using original Brooks Pope and Marcolini (BPM)and modified BPM noise model. A regression-based curve fitting approach has been implemented to predict the shape function in terms of thickness to chord ratio of aerofoils used for blade. For trailing edge height of 0.1% chord, computations for sound power level were done at wind speed of 8 m/s, 17 RPM. The results showed that present approach for thickness correction predicts the noise peak of ∼78dBA at f ∼ 10 kHz which is ∼15dBA lower than that predicted from original BPM. The results were also validated using experiment data from GE 1.5sle, Siemens 2.3 MW turbines with blade lengths between 78 m and 101 m which agreed within 2% at high frequencies, f > 5 kHz. In addition, results from present approach for trailing edge bluntness noise agreed well with modified BPM by Wei et al. at high frequencies, f ∼ 10 kHz where it becomes dominant. The slope of noise curves from present approach, and modified BPM methods are lower when compared with original BPM.
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Conference papers on the topic "Aerofoil Noise"

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Woodhead, Philip C., Tze Pei Chong, Phillip Joseph, Jan G. Wissink, and Paruchuri Chaitanya. "Frequency-Targetable Aerofoil Self-Noise Reduction." In AIAA AVIATION 2021 FORUM. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2021. http://dx.doi.org/10.2514/6.2021-2229.

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Paruchuri, Chaitanya, James R. Gill, Narayanan Subramanian, Phillip Joseph, Christina Vanderwel, Xin Zhang, and Bharathram Ganapathisubramani. "Aerofoil geometry effects on turbulence interaction noise." In 21st AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2015. http://dx.doi.org/10.2514/6.2015-2830.

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Leung, Ronnie, Chaitanya C. Paruchuri, and Phillip Joseph. "Effect of aerofoil thickness on trailing edge noise." In 22nd AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-2814.

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Deuse, Mathieu, and Richard D. Sandberg. "Parametric study of multiple aerofoil self-noise sources using direct noise computation." In 25th AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2019. http://dx.doi.org/10.2514/6.2019-2681.

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Deuse, Mathieu, and Richard D. Sandberg. "Correction: Parametric study of multiple aerofoil self-noise sources using direct noise computation." In 25th AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2019. http://dx.doi.org/10.2514/6.2019-2681.c1.

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Vathylakis, Alexandros, Chaitanya C. Paruchuri, Tze Pei Chong, and Phillip Joseph. "Sensitivity of aerofoil self-noise reductions to serration flap angles." In 22nd AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-2837.

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Ayton, Lorna J., Matthew Colbrook, Thomas F. Geyer, Paruchuri Chaitanya, and Ennes Sarradj. "Modelling chordwise-varying porosity to reduce aerofoil-turbulence interaction noise." In AIAA AVIATION 2021 FORUM. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2021. http://dx.doi.org/10.2514/6.2021-2190.

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De Gennaro, Michele, Andreas Hueppe, Helmut Kuehnelt, Manfred Kaltenbacher, Theodore E. Simos, George Psihoyios, Ch Tsitouras, and Zacharias Anastassi. "Numerical Prediction of Laminar Instability Noise for NACA 0012 Aerofoil." In NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2011: International Conference on Numerical Analysis and Applied Mathematics. AIP, 2011. http://dx.doi.org/10.1063/1.3636675.

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Lacagnina, Giovanni, Seyed Mohammad Hasheminejad, Chaitanya C. Paruchuri, Phillip Joseph, Tze Pei Chong, and Oksana Stalnov. "Leading edge serrations for the reduction of aerofoil separation self-noise." In 23rd AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2017. http://dx.doi.org/10.2514/6.2017-4169.

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Chong, Tze Pei, Till Biedermann, Oliver Koster, and Seyed Mohammad Hasheminejad. "On the Effect of Leading Edge Serrations on Aerofoil Noise Production." In 2018 AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2018. http://dx.doi.org/10.2514/6.2018-3289.

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