scholarly journals Application of a Beamforming Technique to the Measurement of Airfoil Leading Edge Noise

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Thomas Geyer ◽  
Ennes Sarradj ◽  
Jens Giesler
Keyword(s):  
Microphone Array ◽  
Source Region ◽  
Three Dimensional ◽  
Leading Edge ◽  
Noise Sources ◽  
Aeroacoustic Noise ◽  
Turbulent Inflow ◽  
Array Technology ◽  
Beamforming Technique ◽  
Beamforming Algorithm

The present paper describes the use of microphone array technology and beamforming algorithms for the measurement and analysis of noise generated by the interaction of a turbulent flow with the leading edge of an airfoil. Experiments were performed using a setup in an aeroacoustic wind tunnel, where the turbulent inflow is provided by different grids. In order to exactly localize the aeroacoustic noise sources and, moreover, to separate airfoil leading edge noise from grid-generated noise, the selected deconvolution beamforming algorithm is extended to be used on a fully three-dimensional source region. The result of this extended beamforming are three-dimensional mappings of noise source locations. Besides acoustic measurements, the investigation of airfoil leading edge noise requires the measurement of parameters describing the incident turbulence, such as the intensity and a characteristic length scale or time scale. The method used for the determination of these parameters in the present study is explained in detail. To demonstrate the applicability of the extended beamforming algorithm and the experimental setup as a whole, the noise generated at the leading edge of airfoils made of porous materials was measured and compared to that generated at the leading edge of a common nonporous airfoil.

An Experimental Characterization of the Flow Past an Airfoil in the Wake of a Circular Rod

2002 ◽  
Author(s):  
M. Michard ◽  
M. C. Jacob ◽  
N. Grosjean
Keyword(s):  
Source Region ◽  
Three Dimensional ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Small Scale ◽  
Vortex Identification ◽  
Turbulence Structures ◽  
Flow Past ◽  
Scale Turbulence ◽  
High Reynolds

An experimental study of the flow past an airfoil in the wake of a rod shows that, at high Reynolds numbers, the vortices shed by the rod are strongly stretched and split near the leading edge and affected by small scale turbulence structures. These are shown to enhance three-dimensional effects, and to broaden the spectrum around the shedding frequency. The airfoil leading edge is the dominant acoustic source region. Post-processing tools combining Proper Orthogonal Decomposition and new vortex identification algorithms are applied to PIV measurements in order to extract the main vortical structures from snapshots, and study their variability.

Low Noise FEGV Designed by Numerical Method Based on CFD

2004 ◽  
Author(s):  
Naoki Tsuchiya ◽  
Yoshiya Nakamura ◽  
Shinya Goto ◽  
Hidekazu Kodama ◽  
Osamu Nozaki ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Guide Vane ◽  
Three Dimensional ◽  
Leading Edge ◽  
High Amplitude ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Test Facility ◽  
Noise Sources ◽  
Fan Noise

This paper describes a low noise FEGV (Fan Exit Guide Vane), which is designed by a fan noise prediction method based on CFD. Fan noise is predicted by a hybrid scheme, which is the combination of three-dimensional CFD and three-dimensional linear theory. Characteristics of noise sources are investigated in some kinds of FEGV shapes. High amplitude areas spread not only along the leading edge but also in the span-wise positions along the mid-chord. It is found that high amplitude areas around the mid-chord make an important role in noise generation, and appropriate aft-ward swept angle and span-wise distribution of leaned angle could reduce the amplitude of the noise sources keeping aerodynamic performance. A fan noise test for fan scale models has been conducted at an anechoic test facility in IHI Mizuho to demonstrate noise reduction and performance of low noise FEGV. Noise reduction can be achieved keeping aerodynamic performance compared to conventional straight FEGV.

Research on Effect of Noise Emission from Railway Viaduct on Noise Reduction of Noise Barriers

2012 ◽  
Vol 433-440 ◽  
pp. 1852-1856
Author(s):  
Lei Ming Song ◽  
Shou Guang Sun ◽  
Xin Hua Zhang
Keyword(s):  
Noise Reduction ◽  
Microphone Array ◽  
Field Testing ◽  
Vibration Testing ◽  
Noise Emission ◽  
Noise Sources ◽  
Noise Barriers ◽  
Sources Identification ◽  
Array Technology ◽  
Noise Barrier

Noise sources identification based on microphone array theory was firstly introduced, A method was derived, which can be used to analyze effect of noise emission from railway viaduct to noise reduction of noise barriers. Vibration and noise emission of railway viaduct and noise barrier were studied using field testing with microphone array technology and vibration testing. The results concluded that noise emission from the viaduct has remarkable effects on noise reduction of noise barriers compared with the effects of noise emission from the noise barriers themselves, which is neglectable.

scholarly journals A comparison between aeroacoustic source mapping techniques for the characterisation of wind turbine blade models with microphone arrays

ACTA IMEKO ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 147
Author(s):  
Gianmarco Battista ◽  
Marcello Vanali ◽  
Paolo Chiariotti ◽  
Paolo Castellini
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Microphone Array ◽  
Wind Turbine Blade ◽  
Operating Conditions ◽  
Noise Sources ◽  
Aeroacoustic Noise ◽  
Array Measurements ◽  
Mapping Techniques ◽  
Acoustic Mapping

<p class="Abstract">Characterising the aeroacoustic noise sources generated by a rotating wind turbine blade provides useful information for tackling noise reduction of this mechanical system. In this context, microphone array measurements and acoustic source mapping techniques are powerful tools for the identification of aeroacoustic noise sources. This paper discusses a series of acoustic mapping strategies that can be exploited in this kind of applications. A single-blade rotor was tested in a semi-anechoic chamber using a circular microphone array. <br />The Virtual Rotating Array (VRA) approach, which transforms the signals acquired by the physical static array into signals of virtual microphones synchronously rotating with the blade, hence ensuring noise-source stationarity, was used to enable the use of frequency domain acoustic mapping techniques. A comparison among three different acoustic mapping methods is presented: Conventional Beamforming, CLEAN-SC and Covariance Matrix Fitting based on Iterative Re-weighted Least Squares and Bayesian approach. The latter demonstrated to provide the best results for the application and made it possible a detailed characterization of the noise sources generated by the rotating blade at different operating conditions.</p>

scholarly journals Comparison of beamforming algorithms based on localization of calibrating sound sources and air jet noise

2018 ◽  
Vol 7 (2.23) ◽  
pp. 119 ◽  
Author(s):  
V Ershov ◽  
V V. Palchikovskiy
Keyword(s):  
Microphone Array ◽  
Jet Noise ◽  
Point Sources ◽  
Good Work ◽  
Noise Sources ◽  
Sound Sources ◽  
Air Jet ◽  
Good Ability ◽  
Static Point ◽  
Beamforming Algorithm

The paper considers study of beamforming algorithms for localization of noise sources. The mathematical formulations are briefly described for the following algorithms: Delay-and-Sum Beamforming, Cross-spectral Beamforming, Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS). Based on the mentioned algorithms the program codes were developed. Operability of the program codes was tested on virtual localization of the point sources. All algorithms demonstrated good ability to distinguish these sources at different frequencies at their close position relative to each other. Initially, experiments were based on localization of calibrating static sound sources (beepers) using Bruel & Kjaer 54-microphone array. The measured data were processed both in the Bruel & Kjaer software and in the developed software. For static point sources, all algorithms have shown good work quality. The experiments were also carried out for the localization of noise sources in a turbulent air jet. In this case, the best results were demonstrated by Cross-Spectral Beamforming algorithm.  

scholarly journals Effect of a pylon on the broadband noise sources of counter-rotating turbomachinery

2021 ◽  
pp. 1475472X2110551
Author(s):  
Kristóf Tokaji ◽  
Csaba Horváth
Keyword(s):  
Noise Source ◽  
Microphone Array ◽  
Measurement Data ◽  
Leading Edge ◽  
Broadband Noise ◽  
Noise Sources ◽  
Noise Characteristics ◽  
Open Rotor ◽  
Blade Tip ◽  
Generation Mechanisms

Pylons are commonly used for the mounting of engines in the aircraft industry. On the other hand, the installation of a pylon influences the noise generation mechanisms and therefore alters the broadband noise characteristics of a given turbomachinery setup. In this investigation, a counter-rotating open rotor with and without a pylon is investigated in order to determine its effects on broadband noise sources. The various broadband noise sources and their typical frequency ranges have been determined using beamforming maps and spectral analysis. In order to attain a clear impression regarding the broadband noise sources, the Double Filtering beamforming method has been utilized in the investigation. This method removes the tonal components from the recorded signal of a microphone array, resulting in a purely broadband signal. Using beamforming maps, the dominant broadband noise source amplitudes and locations can therefore be investigated in great detail. Compared to other methods, the investigation of measurement data and beamforming maps helps determine the amplitude, the frequency range, and the significance of the various types of broadband noise sources that are truly present in the emitted noise. It has been found for lower frequencies, that the broadband noise sources at the blade root of the aft rotor are dominant, while for higher frequencies, the significant broadband noise sources are localized to the trailing edge region of the forward rotor and the leading edge of the aft rotor. The installation of a pylon has resulted in an additional broadband noise source appearing at the blade tip of the aft rotor.

Selection of a leading edge noise prediction method for PNoise

2018 ◽  
pp. 214-223
Author(s):  
AM Faria ◽  
MM Pimenta ◽  
JY Saab Jr. ◽  
S Rodriguez
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Prediction Method ◽  
Leading Edge ◽  
Wind Farms ◽  
Broadband Noise ◽  
Turbulence Energy ◽  
Noise Prediction ◽  
Migration Routes ◽  
Turbulent Inflow

Wind energy expansion is worldwide followed by various limitations, i.e. land availability, the NIMBY (not in my backyard) attitude, interference on birds migration routes and so on. This undeniable expansion is pushing wind farms near populated areas throughout the years, where noise regulation is more stringent. That demands solutions for the wind turbine (WT) industry, in order to produce quieter WT units. Focusing in the subject of airfoil noise prediction, it can help the assessment and design of quieter wind turbine blades. Considering the airfoil noise as a composition of many sound sources, and in light of the fact that the main noise production mechanisms are the airfoil self-noise and the turbulent inflow (TI) noise, this work is concentrated on the latter. TI noise is classified as an interaction noise, produced by the turbulent inflow, incident on the airfoil leading edge (LE). Theoretical and semi-empirical methods for the TI noise prediction are already available, based on Amiet’s broadband noise theory. Analysis of many TI noise prediction methods is provided by this work in the literature review, as well as the turbulence energy spectrum modeling. This is then followed by comparison of the most reliable TI noise methodologies, qualitatively and quantitatively, with the error estimation, compared to the Ffowcs Williams-Hawkings solution for computational aeroacoustics. Basis for integration of airfoil inflow noise prediction into a wind turbine noise prediction code is the final goal of this work.

scholarly journals Transcriptome Analyses of Myometrium from Fibroid Patients Reveals Phenotypic Differences Compared to Non-Diseased Myometrium

2021 ◽  
Vol 22 (7) ◽  
pp. 3618
Author(s):  
Emmanuel N. Paul ◽  
Gregory W. Burns ◽  
Tyler J. Carpenter ◽  
Joshua A. Grey ◽  
Asgerally T. Fazleabas ◽  
...  
Keyword(s):  
Uterine Fibroid ◽  
Three Dimensional ◽  
Uterine Fibroids ◽  
Principal Component ◽  
Leading Edge ◽  
Gene Set Enrichment ◽  
Phenotypic Differences ◽  
False Discovery ◽  
Gene Sets ◽  
High Concordance

Uterine fibroid tissues are often compared to their matched myometrium in an effort to understand their pathophysiology, but it is not clear whether the myometria of uterine fibroid patients represent truly non-disease control tissues. We analyzed the transcriptomes of myometrial samples from non-fibroid patients (M) and compared them with fibroid (F) and matched myometrial (MF) samples to determine whether there is a phenotypic difference between fibroid and non-fibroid myometria. Multidimensional scaling plots revealed that M samples clustered separately from both MF and F samples. A total of 1169 differentially expressed genes (DEGs) (false discovery rate < 0.05) were observed in the MF comparison with M. Overrepresented Gene Ontology terms showed a high concordance of upregulated gene sets in MF compared to M, particularly extracellular matrix and structure organization. Gene set enrichment analyses showed that the leading-edge genes from the TGFβ signaling and inflammatory response gene sets were significantly enriched in MF. Overall comparison of the three tissues by three-dimensional principal component analyses showed that M, MF, and F samples clustered separately from each other and that a total of 732 DEGs from F vs. M were not found in the F vs. MF, which are likely understudied in the pathogenesis of uterine fibroids and could be key genes for future investigation. These results suggest that the transcriptome of fibroid-associated myometrium is different from that of non-diseased myometrium and that fibroid studies should consider using both matched myometrium and non-diseased myometrium as controls.

scholarly journals Aeroacoustic noise reduction by application of end plates on wall-mounted finite airfoils

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
Erik Schneehagen ◽  
Thomas F. Geyer ◽  
Ennes Sarradj ◽  
Danielle J. Moreau
Keyword(s):  
Noise Reduction ◽  
Microphone Array ◽  
Boundary Layer Transition ◽  
Tip Vortex ◽  
Layer Transition ◽  
Aeroacoustic Noise ◽  
End Plate ◽  
Array Measurements ◽  
Field Noise ◽  
Naca 0012

Abstract One known method to reduce vortex shedding from the tip of a blade is the use of end plates or winglets. Although the aerodynamic impact of such end plates has been investigated in the past, no studies exist on the effect of such end plates on the far-field noise. The aeroacoustic noise reduction of three different end-plate geometries is experimentally investigated. The end plates are applied to the free end of a wall-mounted symmetric NACA 0012 airfoil and a cambered NACA 4412 airfoil with an aspect ratio of 2 and natural boundary layer transition. Microphone array measurements are taken in the aeroacoustic open-jet wind tunnel at BTU Cottbus-Senftenberg for chord-based Reynolds numbers between 75,000 and 225,000 and angles of attack from 0$$^\circ$$ ∘ to 30$$^\circ$$ ∘ . The obtained acoustic spectra show a broad frequency hump for the airfoil base configurations at higher angles of attack that is attributed to tip noise. Hot-wire measurements taken for one configuration show that the application of an end plate diffuses the vorticity at the tip. The aeroacoustic noise contribution of the tip can be reduced when the endplates are applied. This reduction is most effective for higher angles of attack, when the tip vortex is the dominant sound source. Graphic abstract

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