Pub Date : 2022-02-26DOI: 10.1177/1475472X221079549
Hanbo Jiang, Siyang Zhong, Xin Zhang, Xun Huang
Multi-rotor powered drones and urban mobility vehicles (UMV) have received considerable attention over recent years and attracted ever-increasing interest in their aerodynamic noise. Physics-based prediction tools for aerodynamic noise are of importance to facilitate quiet drone designs. In this work, a boundary element method (BEM) based solver is employed to evaluate the scattering of the rotor noise of a flying drone fuselage. The possible non-uniqueness of the solution is tackled using a Combined Helmholtz Interior integral Equation Formulation (CHIEF). The proposed method is applied to evaluate the noise scattering by a realistic fuselage configuration. Results suggest that the fuselage can visibly redirect propeller noise radiation at low frequencies because of wave diffractions. The fuselage can also affect the sound field by wave reflections at high frequencies, producing an apparent noise reduction.
{"title":"Boundary element analysis on the fuselage scattering of drone noise","authors":"Hanbo Jiang, Siyang Zhong, Xin Zhang, Xun Huang","doi":"10.1177/1475472X221079549","DOIUrl":"https://doi.org/10.1177/1475472X221079549","url":null,"abstract":"Multi-rotor powered drones and urban mobility vehicles (UMV) have received considerable attention over recent years and attracted ever-increasing interest in their aerodynamic noise. Physics-based prediction tools for aerodynamic noise are of importance to facilitate quiet drone designs. In this work, a boundary element method (BEM) based solver is employed to evaluate the scattering of the rotor noise of a flying drone fuselage. The possible non-uniqueness of the solution is tackled using a Combined Helmholtz Interior integral Equation Formulation (CHIEF). The proposed method is applied to evaluate the noise scattering by a realistic fuselage configuration. Results suggest that the fuselage can visibly redirect propeller noise radiation at low frequencies because of wave diffractions. The fuselage can also affect the sound field by wave reflections at high frequencies, producing an apparent noise reduction.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"21 1","pages":"43 - 56"},"PeriodicalIF":1.0,"publicationDate":"2022-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45431413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-23DOI: 10.1177/1475472X221079542
E. Guseva, Y. Egorov
The paper presents validation results of a hybrid simulation method for aeroacoustics in turbulent flows at low Mach numbers. The hybrid method implemented in the Ansys Fluent® CFD package applies a scale-resolving turbulence model to compute the noise sources in an incompressible flow, while the noise propagation is modeled by a wave equation formulated for the acoustic potential. The selected test case deals with a flow and a sound field around a generic side view mirror of a car. The SBES model by Menter, which belongs to the class of the RANS-LES models, is used for the flow simulation. It switches to the Large Eddy Simulation (LES) mode in separated mixing layers and recirculation zone behind the mirror as well as in the following wake, where flow develops intensive turbulence and dominating noise sources. The acoustics wave equation is formulated in the model form of Kaltenbacher et al. and is applied in the time domain. The overall calculation is performed as a transient co-simulation on the same mesh using the finite-volume discretization method for both the flow and the acoustics parts. The wave equation is advanced in time using the HHT-α method. Obtained distribution of the mean wall pressure over the mirror surface closely matches the experimental one. Rich content of the resolved turbulent vortices in the separation zone and good agreement of the calculated and measured wall pressure spectra at sensor locations downstream the mirror evidence a proper LES resolution quality of noise sources. Comparison of the computed noise spectra at the remote microphones with the experimental data demonstrates the sound propagation accuracy and validates the overall aeroacoustics simulation method.
{"title":"Application of LES combined with a wave equation for the simulation of noise induced by a flow past a generic side mirror","authors":"E. Guseva, Y. Egorov","doi":"10.1177/1475472X221079542","DOIUrl":"https://doi.org/10.1177/1475472X221079542","url":null,"abstract":"The paper presents validation results of a hybrid simulation method for aeroacoustics in turbulent flows at low Mach numbers. The hybrid method implemented in the Ansys Fluent® CFD package applies a scale-resolving turbulence model to compute the noise sources in an incompressible flow, while the noise propagation is modeled by a wave equation formulated for the acoustic potential. The selected test case deals with a flow and a sound field around a generic side view mirror of a car. The SBES model by Menter, which belongs to the class of the RANS-LES models, is used for the flow simulation. It switches to the Large Eddy Simulation (LES) mode in separated mixing layers and recirculation zone behind the mirror as well as in the following wake, where flow develops intensive turbulence and dominating noise sources. The acoustics wave equation is formulated in the model form of Kaltenbacher et al. and is applied in the time domain. The overall calculation is performed as a transient co-simulation on the same mesh using the finite-volume discretization method for both the flow and the acoustics parts. The wave equation is advanced in time using the HHT-α method. Obtained distribution of the mean wall pressure over the mirror surface closely matches the experimental one. Rich content of the resolved turbulent vortices in the separation zone and good agreement of the calculated and measured wall pressure spectra at sensor locations downstream the mirror evidence a proper LES resolution quality of noise sources. Comparison of the computed noise spectra at the remote microphones with the experimental data demonstrates the sound propagation accuracy and validates the overall aeroacoustics simulation method.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"21 1","pages":"6 - 21"},"PeriodicalIF":1.0,"publicationDate":"2022-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46966149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-01DOI: 10.1177/1475472X211052699
T. Patel, Alexander J. Lilley, Weiqi Shen, Christian Porrello, A. Schindler-Tyka, Subrata Roy, W. Lear, Steven A. E. Miller
Blade vortex interaction noise is a problematic and dominant component of rotor noise. Plasma actuators strategically placed at the tip of the rotor blades can reduce the strength of the tip vortices. This reduction has the potential to significantly reduce blade vortex interaction noise. A combined experimental, numerical, and theoretical program shows supporting evidence that low power plasma actuators can effectively lower coherence of the blade tip vortex and reduce blade vortex interaction noise over-pressure by up to 80%. For a nominal small five-bladed unmanned aerial vehicle, we predict an approximate 8.88 maximum ΔdB reduction for a 150 m/s tip speed. Experimental, computational, and acoustic modeling support these predictions. This study represents a fundamental investigation in the fixed-frame, which provides evidence for higher level research and testing in a rotating framework.
{"title":"Fundamental investigation using active plasma control to reduce blade–vortex interaction noise","authors":"T. Patel, Alexander J. Lilley, Weiqi Shen, Christian Porrello, A. Schindler-Tyka, Subrata Roy, W. Lear, Steven A. E. Miller","doi":"10.1177/1475472X211052699","DOIUrl":"https://doi.org/10.1177/1475472X211052699","url":null,"abstract":"Blade vortex interaction noise is a problematic and dominant component of rotor noise. Plasma actuators strategically placed at the tip of the rotor blades can reduce the strength of the tip vortices. This reduction has the potential to significantly reduce blade vortex interaction noise. A combined experimental, numerical, and theoretical program shows supporting evidence that low power plasma actuators can effectively lower coherence of the blade tip vortex and reduce blade vortex interaction noise over-pressure by up to 80%. For a nominal small five-bladed unmanned aerial vehicle, we predict an approximate 8.88 maximum ΔdB reduction for a 150 m/s tip speed. Experimental, computational, and acoustic modeling support these predictions. This study represents a fundamental investigation in the fixed-frame, which provides evidence for higher level research and testing in a rotating framework.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"870 - 900"},"PeriodicalIF":1.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42319364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-01DOI: 10.1177/1475472x211061782
Dr. Vishnu R. Unni is an Associate Research Scholar in the Department of Mechanical and Aerospace Engineering, Princeton University working with Prof. C. K. Law. Prior to this, he was a Postdoctoral Fellow in Department. of Mechanical and Aerospace Engineering at the University of California San Diego, working with Prof. Abhishek Saha (2018–2020). He received his dual degree (B Tech and M Tech) and PhD, in Aerospace Engineering, from Indian Institute of Technology Madras in 2013 and 2017, respectively. His PhD advisor at IIT Madras was Prof. RI Sujith. Dr. Unni’s research interests include, thermoacoustics, nonlinear dynamics and complex systems theory.
Vishnu R. Unni博士是普林斯顿大学机械与航空航天工程系的副研究员，与C. K. Law教授合作。在此之前，他是该系博士后研究员。加州大学圣地亚哥分校机械与航空航天工程专业，与Abhishek Saha教授合作(2018-2020)。他分别于2013年和2017年在马德拉斯印度理工学院获得航空航天工程双学位(理工学士和理工硕士)和博士学位。他在印度理工学院马德拉斯的博士导师是RI Sujith教授。他的研究兴趣包括热声学、非线性动力学和复杂系统理论。
{"title":"Guest editor biographies","authors":"","doi":"10.1177/1475472x211061782","DOIUrl":"https://doi.org/10.1177/1475472x211061782","url":null,"abstract":"Dr. Vishnu R. Unni is an Associate Research Scholar in the Department of Mechanical and Aerospace Engineering, Princeton University working with Prof. C. K. Law. Prior to this, he was a Postdoctoral Fellow in Department. of Mechanical and Aerospace Engineering at the University of California San Diego, working with Prof. Abhishek Saha (2018–2020). He received his dual degree (B Tech and M Tech) and PhD, in Aerospace Engineering, from Indian Institute of Technology Madras in 2013 and 2017, respectively. His PhD advisor at IIT Madras was Prof. RI Sujith. Dr. Unni’s research interests include, thermoacoustics, nonlinear dynamics and complex systems theory.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"869 - 869"},"PeriodicalIF":1.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44995053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-01DOI: 10.1177/1475472X211052701
S. Redonnet
In regard to the mitigation of environmental noise across major industry sectors, the present study focuses on the numerical prediction of passive noise reduction devices. Here, it is further explored how the noise attenuation induced by locally reacting noise absorbing materials (also called acoustic liners) can be simulated using a time domain highly accurate Computational AeroAcoustics (CAA) method. To this end, it is assessed how a classical Time Domain Impedance Boundary Condition (TDIBC) can effectively model acoustic liners of practical interest, including when the latter are exposed to realistic conditions (grazing flow and noise excitation). The investigation consists in numerically reproducing two experimental campaigns initially performed at NASA Langley Research Center. Two different materials are considered (honeycomb superimposed with perforate or wiremesh resistive face-sheet), each being characterized by a specific noise attenuation behaviour (e.g. dependency on the flow conditions and/or noise excitation). Each material is tested under various flow conditions (e.g. grazing flow of Mach up to 0.5) and/or noise source excitation (e.g. multiple tones of level up to 140 dB each). The results demonstrate the ability of the underlying CAA/TDIBC approach to simulate realistic acoustic liners in non-trivial configurations, with enough physical accuracy (e.g. correct capture of the noise attenuation characteristics) and numerical robustness (e.g. absence of instabilities). The study also reveals that, independent from the CAA/TDIBC approach itself, some specific pre-processing tasks (e.g. impedance eduction and subsequent TDIBC calibration) may play a bigger role than expected, in practice.
{"title":"Further assessment of a time domain impedance boundary condition for the numerical simulation of noise-absorbing materials","authors":"S. Redonnet","doi":"10.1177/1475472X211052701","DOIUrl":"https://doi.org/10.1177/1475472X211052701","url":null,"abstract":"In regard to the mitigation of environmental noise across major industry sectors, the present study focuses on the numerical prediction of passive noise reduction devices. Here, it is further explored how the noise attenuation induced by locally reacting noise absorbing materials (also called acoustic liners) can be simulated using a time domain highly accurate Computational AeroAcoustics (CAA) method. To this end, it is assessed how a classical Time Domain Impedance Boundary Condition (TDIBC) can effectively model acoustic liners of practical interest, including when the latter are exposed to realistic conditions (grazing flow and noise excitation). The investigation consists in numerically reproducing two experimental campaigns initially performed at NASA Langley Research Center. Two different materials are considered (honeycomb superimposed with perforate or wiremesh resistive face-sheet), each being characterized by a specific noise attenuation behaviour (e.g. dependency on the flow conditions and/or noise excitation). Each material is tested under various flow conditions (e.g. grazing flow of Mach up to 0.5) and/or noise source excitation (e.g. multiple tones of level up to 140 dB each). The results demonstrate the ability of the underlying CAA/TDIBC approach to simulate realistic acoustic liners in non-trivial configurations, with enough physical accuracy (e.g. correct capture of the noise attenuation characteristics) and numerical robustness (e.g. absence of instabilities). The study also reveals that, independent from the CAA/TDIBC approach itself, some specific pre-processing tasks (e.g. impedance eduction and subsequent TDIBC calibration) may play a bigger role than expected, in practice.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"927 - 958"},"PeriodicalIF":1.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44752261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-01DOI: 10.1177/1475472X211055178
Kristóf Tokaji, Csaba Horváth
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.
{"title":"Effect of a pylon on the broadband noise sources of counter-rotating turbomachinery","authors":"Kristóf Tokaji, Csaba Horváth","doi":"10.1177/1475472X211055178","DOIUrl":"https://doi.org/10.1177/1475472X211055178","url":null,"abstract":"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.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"979 - 1002"},"PeriodicalIF":1.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49468025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-01DOI: 10.1177/1475472X211055179
A. Aihara, K. Bolin, A. Goude, H. Bernhoff
This study investigates the numerical prediction for the aerodynamic noise of the vertical axis wind turbine using large eddy simulation and the acoustic analogy. Low noise designs are required especially in residential areas, and sound level generated by the wind turbine is therefore important to estimate. In this paper, the incompressible flow field around the 12 kW straight-bladed vertical axis wind turbine with the rotor diameter of 6.5 m is solved, and the sound propagation is calculated based on the Ffowcs Williams and Hawkings acoustic analogy. The sound pressure for the turbine operating at high tip speed ratio is predicted, and it is validated by comparing with measurement. The measured spectra of the sound pressure observed at several azimuth angles show the broadband characteristics, and the prediction is able to reproduce the shape of these spectra. While previous works studying small-scaled vertical axis wind turbines found that the thickness noise is the dominant sound source, the loading noise can be considered to be a main contribution to the total sound for this turbine. The simulation also indicates that the received noise level is higher when the blade moves in the downwind than in the upwind side.
{"title":"Aeroacoustic noise prediction of a vertical axis wind turbine using large eddy simulation","authors":"A. Aihara, K. Bolin, A. Goude, H. Bernhoff","doi":"10.1177/1475472X211055179","DOIUrl":"https://doi.org/10.1177/1475472X211055179","url":null,"abstract":"This study investigates the numerical prediction for the aerodynamic noise of the vertical axis wind turbine using large eddy simulation and the acoustic analogy. Low noise designs are required especially in residential areas, and sound level generated by the wind turbine is therefore important to estimate. In this paper, the incompressible flow field around the 12 kW straight-bladed vertical axis wind turbine with the rotor diameter of 6.5 m is solved, and the sound propagation is calculated based on the Ffowcs Williams and Hawkings acoustic analogy. The sound pressure for the turbine operating at high tip speed ratio is predicted, and it is validated by comparing with measurement. The measured spectra of the sound pressure observed at several azimuth angles show the broadband characteristics, and the prediction is able to reproduce the shape of these spectra. While previous works studying small-scaled vertical axis wind turbines found that the thickness noise is the dominant sound source, the loading noise can be considered to be a main contribution to the total sound for this turbine. The simulation also indicates that the received noise level is higher when the blade moves in the downwind than in the upwind side.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"959 - 978"},"PeriodicalIF":1.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49043830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-01DOI: 10.1177/1475472X211042204
D. Sutliff
I am honored to present to the readers this special issue of the International Journal of Aeroacoustics on Acoustic Liners. Acoustic Liners have been studied since the introduction of turbojet engines and implemented shortly thereafter. Currently, almost all commercial turbofan engines nacelles have acoustic liners installed in somemanner. This Special Issue onAcoustic Liners provides 16 papers across a breadth of material – from analytical and numerical modelling to unique test rigs to evaluation of liner concepts. Contributors from academia, government agencies, and industry throughout the international community provide a range of insight. The focus is on the tried-and-true passive liner paradigmwhich continues to be the principal method of achieving noise reduction. The passive liner concept is straightforward – however, higher bypass ratios and shorter engine nacelles in advanced turbofans, as well as continuing demand for increased noise reduction while mitigating any performance impact, necessitates a continual improvement in liner acoustic performance and installation in novel locations. Therefore, continued study by the aeroacoustics community in this area is necessary to maintain our critical contribution to the improvement of the quality of life in communities near airports. I thank the authors for their contributions whose creativity and expertise are the basis of this issue. I sincerely appreciate the reviewers for their time spent in reviews and providing feedback which greatly improved the quality of the papers. I am grateful to the Editor-in-chief, Dr Ganesh Raman, and the International Journal of Aeroacoustics for providing an opportunity for publishing this special issue. In addition, my thanks are extended to Dr Ed Envia, Assistant Editor, who handled the papers for which I was an author.
{"title":"Editorial for special issue on acoustic liners","authors":"D. Sutliff","doi":"10.1177/1475472X211042204","DOIUrl":"https://doi.org/10.1177/1475472X211042204","url":null,"abstract":"I am honored to present to the readers this special issue of the International Journal of Aeroacoustics on Acoustic Liners. Acoustic Liners have been studied since the introduction of turbojet engines and implemented shortly thereafter. Currently, almost all commercial turbofan engines nacelles have acoustic liners installed in somemanner. This Special Issue onAcoustic Liners provides 16 papers across a breadth of material – from analytical and numerical modelling to unique test rigs to evaluation of liner concepts. Contributors from academia, government agencies, and industry throughout the international community provide a range of insight. The focus is on the tried-and-true passive liner paradigmwhich continues to be the principal method of achieving noise reduction. The passive liner concept is straightforward – however, higher bypass ratios and shorter engine nacelles in advanced turbofans, as well as continuing demand for increased noise reduction while mitigating any performance impact, necessitates a continual improvement in liner acoustic performance and installation in novel locations. Therefore, continued study by the aeroacoustics community in this area is necessary to maintain our critical contribution to the improvement of the quality of life in communities near airports. I thank the authors for their contributions whose creativity and expertise are the basis of this issue. I sincerely appreciate the reviewers for their time spent in reviews and providing feedback which greatly improved the quality of the papers. I am grateful to the Editor-in-chief, Dr Ganesh Raman, and the International Journal of Aeroacoustics for providing an opportunity for publishing this special issue. In addition, my thanks are extended to Dr Ed Envia, Assistant Editor, who handled the papers for which I was an author.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"440 - 440"},"PeriodicalIF":1.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65854651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-01DOI: 10.1177/1475472x211052591
A. L. Maldonado, R. Astley
The current trends for next generation turbofan engines are towards shorter nacelles and increased distances between the fan and the outlet guide vanes. This leads to an overall reduction in lined surface areas as well as an increase in the relative importance of the interstage liner, which is the liner placed between the rotor blades and the stator vanes. So far most of the efforts have been on liners for intakes and bypass ducts. The interstage is different in that the liner is subject to a mean flow with a strong swirl component and shear. The SwirlProp code was developed to contribute to understanding and predicting the effect of the swirl on liner attenuation. The code is based on the linearized Euler equations together with the Ingard–Myers boundary condition. An eigenvalue problem is formulated and discretized using a finite difference method. The code is exhaustively compared against predicted values obtained by other methods for uniform, sheared and swirling mean flows and hard-walled and lined ducts. A cross-validation between SwirlProp and an in-house code from Rolls-Royce was carried out for a more realistic case. Also, details on the implementation of the boundary condition are proposed and details are presented.
{"title":"SwirlProp: A tool for sound propagation and attenuation in swirling flows","authors":"A. L. Maldonado, R. Astley","doi":"10.1177/1475472x211052591","DOIUrl":"https://doi.org/10.1177/1475472x211052591","url":null,"abstract":"The current trends for next generation turbofan engines are towards shorter nacelles and increased distances between the fan and the outlet guide vanes. This leads to an overall reduction in lined surface areas as well as an increase in the relative importance of the interstage liner, which is the liner placed between the rotor blades and the stator vanes. So far most of the efforts have been on liners for intakes and bypass ducts. The interstage is different in that the liner is subject to a mean flow with a strong swirl component and shear. The SwirlProp code was developed to contribute to understanding and predicting the effect of the swirl on liner attenuation. The code is based on the linearized Euler equations together with the Ingard–Myers boundary condition. An eigenvalue problem is formulated and discretized using a finite difference method. The code is exhaustively compared against predicted values obtained by other methods for uniform, sheared and swirling mean flows and hard-walled and lined ducts. A cross-validation between SwirlProp and an in-house code from Rolls-Royce was carried out for a more realistic case. Also, details on the implementation of the boundary condition are proposed and details are presented.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":"20 1","pages":"588 - 609"},"PeriodicalIF":1.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49459862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-01DOI: 10.1177/1475472X211043339
Vianney Masson, S. Moreau, H. Posson, Thomas Nodé-Langlois
Sound transmission through a finite-lined section in a rigid annular duct with swirling and sheared mean flow is analyzed with a new mode-matching method based on the conservation of the total enthalpy and the mass flow, which does not reduce to the conservation of the pressure and the axial velocity when the swirl is non-zero. It relies on a new projection method based on the property of the Chebyshev polynomials and on the scattering matrix formalism to yield transmission losses. This new method is first validated against a finite elements method tool in the uniform axial flow case, and then provides a parametric study of the effect of swirl. At low azimuthal mode order m , the swirl amplifies the attenuation of the contra-rotating modes and makes the attenuation of the co-rotating modes decrease with a trend of a general shift of the transmission loss curve toward contra-rotating modes. A small rotation of the transmission loss curves at low | m | is also generally observed. The boundary condition in the lined section has a small effect on the transmission loss, except close to the cut-on thresholds. Finally, the duct boundary-layer thickness has a significant effect on the cut-on modes and the transmission loss but not its profile.
采用基于总焓守恒和质量流守恒的模式匹配方法，分析了具有旋流和剪切平均流的刚性环形风管在有限衬里截面上的声场传递。当旋流为非零时，总焓和质量流守恒不简化为压力和轴向速度守恒。它依靠一种基于切比雪夫多项式性质和散射矩阵形式的新投影方法来产生传输损耗。该方法首先在均匀轴流情况下通过有限元工具进行了验证，然后对旋流的影响进行了参数化研究。在低方位角模阶m处，旋流放大了对转模的衰减，使同转模的衰减减小，传输损耗曲线总体向对转模方向移动。在低| m |处，透射损耗曲线也普遍观察到小的旋转。在线段的边界条件对传输损耗的影响很小，除了接近接通阈值。最后，管道边界层厚度对导通模态和传输损耗有显著影响，但对其分布无显著影响。
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