The Experts below are selected from a list of 26883 Experts worldwide ranked by ideXlab platform
Jae Wook Kim - One of the best experts on this subject based on the ideXlab platform.
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aerofoil Broadband Noise reductions through double wavelength leading edge serrations a new control concept
Journal of Fluid Mechanics, 2018Co-Authors: Paruchuri Chaitanya, Phillip Joseph, S Narayanan, Jae Wook KimAbstract: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.
Phillip Joseph - One of the best experts on this subject based on the ideXlab platform.
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aerofoil Broadband Noise reductions through double wavelength leading edge serrations a new control concept
Journal of Fluid Mechanics, 2018Co-Authors: Paruchuri Chaitanya, Phillip Joseph, S Narayanan, Jae Wook KimAbstract: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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Relative importance of open rotor tone and Broadband Noise sources
17th AIAA CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), 2011Co-Authors: Michael Kingan, Vincent P. Blandeau, Brian J. Tester, Phillip Joseph, Anthony B. ParryAbstract:A study is made of the Noise levels and spectral characteristics of three contra-rotating propeller rigs: rig 140 tested in 1989, rig 145 build 1 tested in 2008, and rig 145 build 2 tested in 2010. We use tone deletion techniques, applied to the inflow microphone data, to show the relative importance of propeller Broadband Noise to propeller tones with increasing frequency and, in particular, that by the time we reach only moderate frequencies, the one third octave spectra become dominated by the Broadband Noise components. We also show that the Broadband Noise continues to be important as blade speed and rig thrust are varied and that these spectral characteristics are present on both modern and older contra-rotating propeller designs – even those with a profusion of tones and strong tone protusion. We also show how the tone and Broadband Noise levels have reduced with more recent, and aeroacoustically improved, blade designs
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Broadband Noise due to rotor wake rotor interaction in contra rotating open rotors
AIAA Journal, 2010Co-Authors: Vincent P. Blandeau, Phillip JosephAbstract:A semi-analytical model for the prediction of the Broadband Noise due to the interaction between turbulent rotor wakesandarotorincontra-rotatingopenrotorsispresented.Theunsteadyloadingoftherearrotorismodeledusing classicalisolated flat-platetheory.Striptheoryisusedtotreatthespanwisevariationsofaerodynamicquantitiesand blade geometry. The turbulent wake is assumed to be homogeneous and isotropic turbulence that is modulated by a train of wake profiles. The model is presented in detail and insight into its modal behavior is provided. A parameter study is conducted to investigate the effects of blade number, rotor–rotor gap and rotor speeds on Broadband Noise emissions due to rotor–wake/rotor interaction in contra-rotating open rotors. Scaling laws for sound power levels have been established analytically and show good agreement with the results of the parameter study. Nomenclature a = empirical wake parameter Bi = blade number of theith rotor bW = half-wake width, m Cd = drag coefficient of front airfoils c0 = speed of sound, m:s � 1 ci = blade chord, m cl
Daniele Ragni - One of the best experts on this subject based on the ideXlab platform.
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3d printed perforated trailing edges for Broadband Noise abatement
AIAA CEAS Aeroacoustics Conference, 2019Co-Authors: Rubio A Carpio, Daniele Ragni, Francesco Avallone, Mirjam Snellen, S Van Der ZwaagAbstract:Turbulent boundary layer trailing-edge Noise scattered by a NACA0018 airfoil equipped with 3D printed perforated trailing-edge inserts, i.e. with straight cylindrical channels connecting the two sides of the airfoil, is investigated. The inserts have different permeability in order to assess the effect of this property on Broadband Noise generation. Far-field Noise is measured with a phased microphone array. The experiments are performed at free-stream velocities of 26 and 41 m/s, corresponding to chord-based Reynolds numbers of 3.4x 105 and 5.4x105, and at angles of attack of 0 and 4.8_. The inserts, with permeability values of 1.5x10 -9 and 5.4x10 -9 m2, attenuate respectively up to 5 and 9.5 dB at 0_ and up to 4 and 7.5 dB at 4.8_ incidence. The Noise abatement of inserts with straight passages is compared with that of inserts manufactured using metallic foams with a random pore distribution but similar permeability. It is found that to achieve similar overall Noise attenuation levels, the perforated inserts require at least 3 times higher permeability than the metal foam inserts. From this we conclude that in order to maximize the Noise attenuation potential of permeable inserts, the inner structure of the permeable trailing-edge insert must be considered.
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Benefits of curved serrations on Broadband trailing-edge Noise reduction
Journal of Sound and Vibration, 2017Co-Authors: W. C.p. Van Der Velden, Daniele RagniAbstract:Far-field Noise and flow field over a novel curved trailing-edge serration (named as iron-shaped serration) are investigated. Spectra of the far-field Broadband Noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new design is compared to a conventional trailing-edge serration with a triangular geometry. Both serration geometries were retrofitted to a NACA 0018 airfoil at zero degree angle of attack. The iron-shaped geometry is found to reduce far-field Broadband Noise of approximately 2 dB more than the conventional sawtooth serration for chord-based Strouhal numbers Stc
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Three-dimensional flow field over a trailing-edge serration and implications on Broadband Noise
Physics of Fluids, 2016Co-Authors: S. Pr�bsting, Daniele RagniAbstract:The three-dimensional flow field over the suction side of a NACA 0018 airfoil with trailing-edge serrations was studied by means of time-resolved tomographic particle image velocimetry. Mean flow results show that the boundary layer thickness decreases along the streamwise direction with a corresponding reduction of the size of the turbulent structures developing over the suction side of the serrations. At a positive angle of attack, streamwise-oriented and counter-rotating vortices aligned with the edge of the serrations are found to be the main features of the mean flow field. Their formation is attributed to the pressure imbalance between the two sides of the airfoil and the mixing layer at the edge. They locally modify the effective angle seen by the turbulent flow approaching the serrated edge. This effect may contribute to the serration underperformance in terms of Noise reduction reported in literature. The spatial distribution of the spectra of the source term of the Poisson equation, which relates the velocity field to pressure fluctuations, suggests that the contribution of the serrations to far-field Broadband Noise is a function of the streamwise location. This observation is congruent with the spectra of the wall-normal and spanwise velocity fluctuations, which typically show low intensity close to the tips of the individual serrations. It follows that analytical models must take into account the local contribution to the far-field Noise induced by the streamwise variation of the hydrodynamic pressure on the serration surface.
Thomas J Imig - One of the best experts on this subject based on the ideXlab platform.
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comparison of Noise and tone azimuth tuning of neurons in cat primary auditory cortex and medical geniculate body
Journal of Neurophysiology, 1995Co-Authors: J C Clarey, Frank K Samson, W A Irons, Pascal Barone, Thomas J ImigAbstract:1. A comparison of the azimuth tuning of single neurons to Broadband Noise and to best frequency (BF) tone bursts was made in primary auditory cortex (AI: n = 173) and the medial geniculate body (M...
Paruchuri Chaitanya - One of the best experts on this subject based on the ideXlab platform.
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acat1 benchmark of rans informed analytical methods for fan Broadband Noise prediction part i influence of the rans simulation
Acoustics, 2020Co-Authors: Carolin A Kissner, Paruchuri Chaitanya, Sebastien Guerin, Pascal Seeler, Mattias Billson, Pedro Carrasco Larana, Helene De Laborderie, Benjamin Francois, Katharina Lefarth, Danny LewisAbstract:A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan Broadband Noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan Broadband Noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan Broadband Noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan Broadband Noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.
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aerofoil Broadband Noise reductions through double wavelength leading edge serrations a new control concept
Journal of Fluid Mechanics, 2018Co-Authors: Paruchuri Chaitanya, Phillip Joseph, S Narayanan, Jae Wook KimAbstract: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.
