{"title":"Experimental investigation of the output duct role in the transient bleed valve noise","authors":"P. Laffay, S. Moreau, Marc C. Jacob, J. Regnard","doi":"10.2514/6.2018-3606","DOIUrl":"https://doi.org/10.2514/6.2018-3606","url":null,"abstract":"","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123010932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A key parameter in designing and assessing advanced broadband acoustic liners to achieve the current and future noise reduction goals is the acoustic impedance presented by the liner. This parameter, intrinsic to a specific liner configuration, is dependent on sound pressure level and grazing flow velocity. Current impedance eduction approaches have, in general, provided excellent results and continue to be employed throughout the acoustic liner community. However, some recent applications have indicated a possible dependence of the educed impedance on the direction of incident waves relative to the mean flow. The purpose of the current study is to investigate this unexpected behavior for various impedance eduction methods based on the Pridmore-Brown and convected Helmholtz equations. Specifically, the effects of flow profile and axial wavenumber uncertainties on educed impedances for upstream and downstream sources are investigated. The uniform flow results demonstrate the importance of setting a correct Mach number value in obtaining consistent educed impedances for upstream and downstream sources. In fact, the consistency of results over the two source locations was greatly improved by a slight modification of the uniform flow Mach number. In addition, uncertainty in educed axial wavenumber was also illustrated to correlate well with differences in the educed impedances, even with modified uniform flow Mach number. Finally, while less straightforward than in the uniform flow case, it appears that modification of the mean flow profile may also improve consistency of results for upstream and downstream results when shear flow is included.
{"title":"Assessment of Axial Wave Number and Mean Flow Uncertainty on Acoustic Liner Impedance Eduction","authors":"D. Nark, Michael G. Jones, E. Piot","doi":"10.2514/6.2018-3444","DOIUrl":"https://doi.org/10.2514/6.2018-3444","url":null,"abstract":"A key parameter in designing and assessing advanced broadband acoustic liners to achieve the current and future noise reduction goals is the acoustic impedance presented by the liner. This parameter, intrinsic to a specific liner configuration, is dependent on sound pressure level and grazing flow velocity. Current impedance eduction approaches have, in general, provided excellent results and continue to be employed throughout the acoustic liner community. However, some recent applications have indicated a possible dependence of the educed impedance on the direction of incident waves relative to the mean flow. The purpose of the current study is to investigate this unexpected behavior for various impedance eduction methods based on the Pridmore-Brown and convected Helmholtz equations. Specifically, the effects of flow profile and axial wavenumber uncertainties on educed impedances for upstream and downstream sources are investigated. The uniform flow results demonstrate the importance of setting a correct Mach number value in obtaining consistent educed impedances for upstream and downstream sources. In fact, the consistency of results over the two source locations was greatly improved by a slight modification of the uniform flow Mach number. In addition, uncertainty in educed axial wavenumber was also illustrated to correlate well with differences in the educed impedances, even with modified uniform flow Mach number. Finally, while less straightforward than in the uniform flow case, it appears that modification of the mean flow profile may also improve consistency of results for upstream and downstream results when shear flow is included.","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126275686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents an analytic solution for the sound generated by an unsteady gust interacting with a semi-infinite at plate with a piecewise linear periodic leading edge. The Wiener-Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to allow analytical progress. A fully analytic solution is obtained in terms of a modal expansion for the far-field noise which is obtained by summing only a finite number of cuton modes, allowing very quick evaluation. The analytic solution is compared to experimental results for five test case leading-edge geometries. Good agreement is seen indicating the analytic model is capturing the key features of the interaction such as the destructive interference from the tip and root. In four of the five test cases the serrated edges show large reductions of noise compared to the straight edge at mid and high frequencies, however the square wave geometry is seen to be ineffective at noise reduction for high frequencies.
{"title":"Analytic solutions for reduced leading-edge noise aerofoils","authors":"Lorna J. Ayton, Chaitanya C. Paruchuri","doi":"10.2514/6.2018-3284","DOIUrl":"https://doi.org/10.2514/6.2018-3284","url":null,"abstract":"This paper presents an analytic solution for the sound generated by an unsteady gust interacting with a semi-infinite at plate with a piecewise linear periodic leading edge. The Wiener-Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to allow analytical progress. A fully analytic solution is obtained in terms of a modal expansion for the far-field noise which is obtained by summing only a finite number of cuton modes, allowing very quick evaluation. The analytic solution is compared to experimental results for five test case leading-edge geometries. Good agreement is seen indicating the analytic model is capturing the key features of the interaction such as the destructive interference from the tip and root. In four of the five test cases the serrated edges show large reductions of noise compared to the straight edge at mid and high frequencies, however the square wave geometry is seen to be ineffective at noise reduction for high frequencies.","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120945294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Kadar, S. L. Bras, H. Bériot, C. Schram, V. Korchagin, W. D. Roeck, W. Desmet
{"title":"Airfoil trailing-edge noise prediction combining a random particle-mesh method with a Helmholtz solver","authors":"A. Kadar, S. L. Bras, H. Bériot, C. Schram, V. Korchagin, W. D. Roeck, W. Desmet","doi":"10.2514/6.2018-3596","DOIUrl":"https://doi.org/10.2514/6.2018-3596","url":null,"abstract":"","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125159353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
One way of representing surface pressure fluctuations is to display them in frequency-dependent wavenumber spectra. They can be used to feed structural vibration predictions model. However, mostly models and experimental data from wind tunnel and water tunnel experiments have been employed. Apart from possible scaling effects, only hydrodynamic pressure fluctuations are incorporated in these models. Some data from flight tests exists, but again this data is limited to sections of the aircraft where the hydrodynamic pressure fluctuations are dominant. In order to consider both, acoustic and hydrodynamic surface pressure fluctuations in flight a beamforming approach is used in the following to determine wavenumber spectra of pressure fluctuations in cruise flight. This allows for the simultaneous characterization of both, hydrodynamic and acoustic pressure fluctuations and for the discrimination between the two. The wavenumber spectra can be used directly as input for the prediction of structural vibration.
{"title":"Up in the Air: In-Flight Wavenumber Characterization of Surface Pressure Fluctuations at Transonic Conditions","authors":"S. Haxter, C. Spehr","doi":"10.2514/6.2018-3275","DOIUrl":"https://doi.org/10.2514/6.2018-3275","url":null,"abstract":"One way of representing surface pressure fluctuations is to display them in frequency-dependent wavenumber spectra. They can be used to feed structural vibration predictions model. However, mostly models and experimental data from wind tunnel and water tunnel experiments have been employed. Apart from possible scaling effects, only hydrodynamic pressure fluctuations are incorporated in these models. Some data from flight tests exists, but again this data is limited to sections of the aircraft where the hydrodynamic pressure fluctuations are dominant. In order to consider both, acoustic and hydrodynamic surface pressure fluctuations in flight a beamforming approach is used in the following to determine wavenumber spectra of pressure fluctuations in cruise flight. This allows for the simultaneous characterization of both, hydrodynamic and acoustic pressure fluctuations and for the discrimination between the two. The wavenumber spectra can be used directly as input for the prediction of structural vibration.","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122652329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Integration of Acoustic Installation Effects in Inverse Generalized BeamForming Algorithm","authors":"N. Wyer, D. Logothetis, C. Schram","doi":"10.2514/6.2018-2965","DOIUrl":"https://doi.org/10.2514/6.2018-2965","url":null,"abstract":"","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131402287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yohei Inoue, Tsuyoshi Kanuma, Yuma Tasai, H. Maekawa
{"title":"Effects of Free Stream Disturbance on the Development of the Compressible Flow around a Square Cylinder at Subsonic Mach Numbers","authors":"Yohei Inoue, Tsuyoshi Kanuma, Yuma Tasai, H. Maekawa","doi":"10.2514/6.2018-4105","DOIUrl":"https://doi.org/10.2514/6.2018-4105","url":null,"abstract":"","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131525660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Using the Linearized Navier-Stokes Equations to Model Acoustic Liners","authors":"M. J. H. Jensen, Elin Svensson, K. Shaposhnikov","doi":"10.2514/6.2018-3783","DOIUrl":"https://doi.org/10.2514/6.2018-3783","url":null,"abstract":"","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132361175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Unsteady coherent surface-pressure fluctuations from time-averaged flow data with given two-point statistics","authors":"F. Avallone, D. Casalino, D. Ragni","doi":"10.2514/6.2018-4097","DOIUrl":"https://doi.org/10.2514/6.2018-4097","url":null,"abstract":"","PeriodicalId":429337,"journal":{"name":"2018 AIAA/CEAS Aeroacoustics Conference","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121870510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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