Pub Date : 2023-01-20DOI: 10.1177/1475472X231152608
Samuel Afari, R. Mankbadi
A high-fidelity simulation of two in-line counter-rotating propellers in hover, and in forward flight conditions are performed. Near field flow and acoustic properties were resolved using Hybrid LES-Unsteady RANS. Far-field sound predictions were performed using Ffowcs-Williams-Hawkings formulation. The two-propeller results in hovering are compared with that of the single propeller. This enabled us to identify the aerodynamic changes resulting from the proximity of the two propellers to each other and to understand the mechanisms causing the changes in the radiated sound. We then considered the forward flight case and compared it with the corresponding hovering case. This enabled us to identify the aerodynamic changes resulting from the incoming stream. By examining the near acoustic field, the far-field spectra, the Spectral Proper Orthogonal Decomposition, and by conducting periodic averaging, we were able to identify the sources of the changes to the observed tonal and broadband noise.
对两种对旋螺旋桨在悬停和前飞状态下的高保真仿真进行了研究。采用混合les -非定常RANS对近场流场和声学特性进行了解析。采用ffowcs - williams - hawkins公式进行远场声音预测。对双螺旋桨与单螺旋桨的悬停效果进行了比较。这使我们能够确定由于两个螺旋桨彼此接近而导致的空气动力学变化，并了解导致辐射声音变化的机制。然后，我们考虑了向前飞行的情况，并与相应的悬停情况进行了比较。这使我们能够识别来自流入气流的空气动力学变化。通过检查近声场、远场光谱、光谱固有正交分解以及进行周期性平均，我们能够确定观测到的音调和宽带噪声变化的来源。
{"title":"Simulations of multi-rotor interaction noise at hovering & forward flight conditions","authors":"Samuel Afari, R. Mankbadi","doi":"10.1177/1475472X231152608","DOIUrl":"https://doi.org/10.1177/1475472X231152608","url":null,"abstract":"A high-fidelity simulation of two in-line counter-rotating propellers in hover, and in forward flight conditions are performed. Near field flow and acoustic properties were resolved using Hybrid LES-Unsteady RANS. Far-field sound predictions were performed using Ffowcs-Williams-Hawkings formulation. The two-propeller results in hovering are compared with that of the single propeller. This enabled us to identify the aerodynamic changes resulting from the proximity of the two propellers to each other and to understand the mechanisms causing the changes in the radiated sound. We then considered the forward flight case and compared it with the corresponding hovering case. This enabled us to identify the aerodynamic changes resulting from the incoming stream. By examining the near acoustic field, the far-field spectra, the Spectral Proper Orthogonal Decomposition, and by conducting periodic averaging, we were able to identify the sources of the changes to the observed tonal and broadband noise.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43009820","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 : 2023-01-17DOI: 10.1177/1475472X231152607
Sujit Kumar, Priyanshu Mishra, S. Narayanan
The present paper provides a detailed acoustic characterization of symmetric and asymmetric NACA airfoils for various thickness ratios to determine the best thickness ratio and geometry which provide lower acoustic radiations with respect to the standard NACA0010 airfoil. The studies are conducted for various t/c values of 0.12, 0.15 and 0.21, where t is the airfoil thickness and c is the airfoil chord. The far-field acoustic emissions are observed to decrease with increase in t/c ratios for both the symmetric and asymmetric airfoils. For all the t/c values and jet velocities studied, the asymmetric airfoils show higher noise reductions from mid to high frequencies as compared to the symmetric ones, which might be due to the reduced transverse velocity fluctuations as a result of the large distortions imparted to oncoming turbulent gust by the formation of the larger stagnation pressure zone. The symmetric airfoils show a maximum reduction up to 3 dB from mid to high frequencies while asymmetric ones show a reduction up to about 5 dB. An empirical expression is developed for the ΔOAPWL as a function of t/c only for both the symmetric and asymmetric airfoils, where ΔOAPWL is the overall sound power reduction level in dB. It reveals that the ΔOAPWL follow a second order polynomial for both the symmetric and asymmetric airfoils at all jet velocities studied. It is observed that thicker (i.e., t/c = 0.21) symmetric and asymmetric airfoils show lower acoustic radiations as compared to the thinner ones for all the emission angles. In general, it is observed that the thinner airfoils show higher directivity as compared thicker ones, albeit they show a common trait of downstream directivity. Further the highest directivity is seen at an emission angle of 67.5° for both the symmetric and asymmetric airfoils. Thus, the present study clearly demonstrates that the airfoils with higher t/c ratios could be considered as the best passive means for achieving substantial reductions of airfoil broadband noise over a wide range of frequencies.
{"title":"Investigations of thickness effects on the acoustic characteristics of symmetric and asymmetric airfoils","authors":"Sujit Kumar, Priyanshu Mishra, S. Narayanan","doi":"10.1177/1475472X231152607","DOIUrl":"https://doi.org/10.1177/1475472X231152607","url":null,"abstract":"The present paper provides a detailed acoustic characterization of symmetric and asymmetric NACA airfoils for various thickness ratios to determine the best thickness ratio and geometry which provide lower acoustic radiations with respect to the standard NACA0010 airfoil. The studies are conducted for various t/c values of 0.12, 0.15 and 0.21, where t is the airfoil thickness and c is the airfoil chord. The far-field acoustic emissions are observed to decrease with increase in t/c ratios for both the symmetric and asymmetric airfoils. For all the t/c values and jet velocities studied, the asymmetric airfoils show higher noise reductions from mid to high frequencies as compared to the symmetric ones, which might be due to the reduced transverse velocity fluctuations as a result of the large distortions imparted to oncoming turbulent gust by the formation of the larger stagnation pressure zone. The symmetric airfoils show a maximum reduction up to 3 dB from mid to high frequencies while asymmetric ones show a reduction up to about 5 dB. An empirical expression is developed for the ΔOAPWL as a function of t/c only for both the symmetric and asymmetric airfoils, where ΔOAPWL is the overall sound power reduction level in dB. It reveals that the ΔOAPWL follow a second order polynomial for both the symmetric and asymmetric airfoils at all jet velocities studied. It is observed that thicker (i.e., t/c = 0.21) symmetric and asymmetric airfoils show lower acoustic radiations as compared to the thinner ones for all the emission angles. In general, it is observed that the thinner airfoils show higher directivity as compared thicker ones, albeit they show a common trait of downstream directivity. Further the highest directivity is seen at an emission angle of 67.5° for both the symmetric and asymmetric airfoils. Thus, the present study clearly demonstrates that the airfoils with higher t/c ratios could be considered as the best passive means for achieving substantial reductions of airfoil broadband noise over a wide range of frequencies.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46991682","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 : 2023-01-11DOI: 10.1177/1475472X221150176
A. Karn, Ritvik Anand, Aditya Kataria, R. Donga, Naman Agarwal, V. Singh
The physics of music has been well studied and has provided the basis on which musical instruments are made, studied and characterized. Significant research has been conducted on the different kinds of musical instruments, which range from traditional instruments like the mridangas of India to the bagpipes of Scotland. In fact, a lot of research has been carried on the acoustics of different kinds of flutes as well, such as the Finnish kantele and the Indonesian Kompangs. The Indian subcontinent, the birthplace of transverse flutes and a host of other instruments, itself has a plethora of unique musical instruments that have been scientifically examined. Yet, the Bastar flutes of India have evaded the due scientific attention that they deserve owing to their unique sound generation mechanism. Quite strangely and surprisingly, these Bastar flutes are a unique genre of flutes that don’t require lips to be played, and are quite intriguing. The current research explores the aeroacoustics of a Bastar flute via experimental measurements, computational simulations and analytical formulations. The results demonstrate that the amplitude produced is directly proportional to the number of rims present. This are also responsible for producing a low-frequency, high-amplitude melodious sound. It also suggests that the underlying mechanism behind sound generation in a Bastar flute is a unique blend of edge tone and a jet tone, demonstrating a rare phenomenon not seen in traditional musical instruments. This uncommon phenomenon has the potential to unlock several new applications in the field of acoustics.
{"title":"Playing flute without lips? Tones of music lost in time: An investigation of the indigenous Bastar flutes of India","authors":"A. Karn, Ritvik Anand, Aditya Kataria, R. Donga, Naman Agarwal, V. Singh","doi":"10.1177/1475472X221150176","DOIUrl":"https://doi.org/10.1177/1475472X221150176","url":null,"abstract":"The physics of music has been well studied and has provided the basis on which musical instruments are made, studied and characterized. Significant research has been conducted on the different kinds of musical instruments, which range from traditional instruments like the mridangas of India to the bagpipes of Scotland. In fact, a lot of research has been carried on the acoustics of different kinds of flutes as well, such as the Finnish kantele and the Indonesian Kompangs. The Indian subcontinent, the birthplace of transverse flutes and a host of other instruments, itself has a plethora of unique musical instruments that have been scientifically examined. Yet, the Bastar flutes of India have evaded the due scientific attention that they deserve owing to their unique sound generation mechanism. Quite strangely and surprisingly, these Bastar flutes are a unique genre of flutes that don’t require lips to be played, and are quite intriguing. The current research explores the aeroacoustics of a Bastar flute via experimental measurements, computational simulations and analytical formulations. The results demonstrate that the amplitude produced is directly proportional to the number of rims present. This are also responsible for producing a low-frequency, high-amplitude melodious sound. It also suggests that the underlying mechanism behind sound generation in a Bastar flute is a unique blend of edge tone and a jet tone, demonstrating a rare phenomenon not seen in traditional musical instruments. This uncommon phenomenon has the potential to unlock several new applications in the field of acoustics.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41960252","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 : 2023-01-10DOI: 10.1177/1475472X221150173
Dhanush Vittal-Shenoy, R. Gojon, T. Jardin, Marc C. Jacob
The aeroacoustics of an SD7003 airfoil at Reynolds number 60,000 is investigated using Large Eddy Simulation. Five simulations are performed to study the effects of angle-of-attack and Mach number at fixed Reynolds number. For the three cases with angle-of-attack equal to 0° (M = 0.1, 0.3 and 0.6), a pure tonal noise associated with a 2D organisation of the flow is obtained. This flow topology is due to the establishment of a well known aeroacoustic feedback loop between the separation point on the suction side of the airfoil and the trailing edge. The occurrence of this loop is corroborated by the presence of a standing wave pattern with characteristic mode number in accordance with Panda’s model. The main effect of the Mach number is to promote flow separation and hence increase separation length and mode number. In addition, the first harmonic and the sub-harmonic of the tone, observed in the far field acoustic spectrum, are found to be generated in the wake, presumably due to non-linear vortex interactions. For the two other angles-of-attack 4° and 8° at M = 0.1, the feedback loop does not establish and a Laminar Separation Bubble (LSB) is observed. When increasing the angle-of-attack, the LSB shrinks with earlier reattachment. For those two cases, far-field spectra are characterized by a low frequency associated with the breathing motion of the LSB and the reattachment point fluctuating in space. The frequency of this fluctuation depends on the curvature of the bubble. Far-field spectra are also characterized by a broadband trailing edge noise whose frequency range decreases with the angle-of-attack. Again, this evolution is found to depend on the curvature of the bubble which may promote a centrifugal instability in the separated shear layer.
{"title":"Angle-of-attack and Mach number effects on the aeroacoustics of an SD7003 airfoil at Reynolds number 60,000","authors":"Dhanush Vittal-Shenoy, R. Gojon, T. Jardin, Marc C. Jacob","doi":"10.1177/1475472X221150173","DOIUrl":"https://doi.org/10.1177/1475472X221150173","url":null,"abstract":"The aeroacoustics of an SD7003 airfoil at Reynolds number 60,000 is investigated using Large Eddy Simulation. Five simulations are performed to study the effects of angle-of-attack and Mach number at fixed Reynolds number. For the three cases with angle-of-attack equal to 0° (M = 0.1, 0.3 and 0.6), a pure tonal noise associated with a 2D organisation of the flow is obtained. This flow topology is due to the establishment of a well known aeroacoustic feedback loop between the separation point on the suction side of the airfoil and the trailing edge. The occurrence of this loop is corroborated by the presence of a standing wave pattern with characteristic mode number in accordance with Panda’s model. The main effect of the Mach number is to promote flow separation and hence increase separation length and mode number. In addition, the first harmonic and the sub-harmonic of the tone, observed in the far field acoustic spectrum, are found to be generated in the wake, presumably due to non-linear vortex interactions. For the two other angles-of-attack 4° and 8° at M = 0.1, the feedback loop does not establish and a Laminar Separation Bubble (LSB) is observed. When increasing the angle-of-attack, the LSB shrinks with earlier reattachment. For those two cases, far-field spectra are characterized by a low frequency associated with the breathing motion of the LSB and the reattachment point fluctuating in space. The frequency of this fluctuation depends on the curvature of the bubble. Far-field spectra are also characterized by a broadband trailing edge noise whose frequency range decreases with the angle-of-attack. Again, this evolution is found to depend on the curvature of the bubble which may promote a centrifugal instability in the separated shear layer.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49022594","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 : 2023-01-09DOI: 10.1177/1475472X221150181
T. Jardin, R. Gojon, N. Doué, H. Parisot-Dupuis
We compare medium and high fidelity numerical simulations to experiments conducted on low Reynolds number rotors typical of small scale Unmanned Aircraft Systems (UAS). We first show that these numerical approaches provide reasonable estimates of the aerodynamic performance and farfield tonal noise and hence apply them for the investigation of the influence of solidity ratio on the aerodynamics and acoustics of small scale rotors operating under hovering, iso-thrust conditions. We show that while solidity ratio has a weak impact on aerodynamic performance, it may help drastically reduce farfield tonal noise. This reduction is however found to depend on the interplay between thickness and loading noise such that increasing the solidity by increasing the number of blades at constant blades’ aspect ratio or by decreasing the blades’ aspect ratio keeping the number of blades constant may yield very different, sometimes opposite, trends.
{"title":"Numerical and experimental analysis of the influence of solidity on rotor aeroacoustics at low Reynolds numbers","authors":"T. Jardin, R. Gojon, N. Doué, H. Parisot-Dupuis","doi":"10.1177/1475472X221150181","DOIUrl":"https://doi.org/10.1177/1475472X221150181","url":null,"abstract":"We compare medium and high fidelity numerical simulations to experiments conducted on low Reynolds number rotors typical of small scale Unmanned Aircraft Systems (UAS). We first show that these numerical approaches provide reasonable estimates of the aerodynamic performance and farfield tonal noise and hence apply them for the investigation of the influence of solidity ratio on the aerodynamics and acoustics of small scale rotors operating under hovering, iso-thrust conditions. We show that while solidity ratio has a weak impact on aerodynamic performance, it may help drastically reduce farfield tonal noise. This reduction is however found to depend on the interplay between thickness and loading noise such that increasing the solidity by increasing the number of blades at constant blades’ aspect ratio or by decreasing the blades’ aspect ratio keeping the number of blades constant may yield very different, sometimes opposite, trends.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48142042","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 : 2023-01-03DOI: 10.1177/1475472X221150170
Harinath Reddy Nakkala, Krishnamurthy Srinivasan
The offset jet configuration is one where the jet is discharged at some distance from a solid surface. Although the geometric configuration may look simple, the flow may involve several complexities. In propulsion systems, the high-speed jet generated from the rear engine of an aircraft, flowing nearby the fuselage, can be treated as an offset jet. In this work, an experimental investigation of the interaction noise due to circular high-speed offset jets is performed in an anechoic environment at different nozzle pressure ratios and offset ratios (height of the jet centerline above the plate per nozzle width). A large horizontal plate placed over a height-adjustable stand is used as the offset plate. Acoustic characteristics such as overall sound pressure level and the directivity pattern of free and offset jets are compared for different nozzle pressure ratios. The effect of offset ratio on noise characteristics is also investigated. Flow visualization is also carried out to understand the shock structure and its noise generation mechanism. Acoustic characteristics reveal that noise levels are higher for an offset jet compared to a free jet. Sound pressure levels for offset ratio 0.5 are lower than those for other offset ratios. The noise levels are higher for offset ratio 1.0 due to the presence of feedback tone. Schlieren visualization studies also corroborate the above characteristics.
{"title":"Aeroacoustic characteristics of supersonic offset jets","authors":"Harinath Reddy Nakkala, Krishnamurthy Srinivasan","doi":"10.1177/1475472X221150170","DOIUrl":"https://doi.org/10.1177/1475472X221150170","url":null,"abstract":"The offset jet configuration is one where the jet is discharged at some distance from a solid surface. Although the geometric configuration may look simple, the flow may involve several complexities. In propulsion systems, the high-speed jet generated from the rear engine of an aircraft, flowing nearby the fuselage, can be treated as an offset jet. In this work, an experimental investigation of the interaction noise due to circular high-speed offset jets is performed in an anechoic environment at different nozzle pressure ratios and offset ratios (height of the jet centerline above the plate per nozzle width). A large horizontal plate placed over a height-adjustable stand is used as the offset plate. Acoustic characteristics such as overall sound pressure level and the directivity pattern of free and offset jets are compared for different nozzle pressure ratios. The effect of offset ratio on noise characteristics is also investigated. Flow visualization is also carried out to understand the shock structure and its noise generation mechanism. Acoustic characteristics reveal that noise levels are higher for an offset jet compared to a free jet. Sound pressure levels for offset ratio 0.5 are lower than those for other offset ratios. The noise levels are higher for offset ratio 1.0 due to the presence of feedback tone. Schlieren visualization studies also corroborate the above characteristics.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47939555","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 : 2023-01-03DOI: 10.1177/1475472X221150180
Ye Li, Xin-biao Xiao, Yumei Zhang, Zhao Tang, Aipeng Pan
In this study, porous sound-absorbing materials used as a lining in double-panel structure applications (such as high-speed train body structures) to limit flow-induced vibration interior noise were studied, and acoustic optimization design was performed. First, in the wavenumber domain, the cross-spectrum Corcos model was used to characterize the dynamic hydrodynamic pressure of turbulence. Biot’s theory is used to model the porous materials. The transmission loss (TL) of the sandwich panel were also determined based on the model superposition method. Three types of sandwich panel structures were considered: air–air (A–A), bonded-bonded (B–B), and bonded-air (B–A). The TL of the three structure types under hydrodynamic pressure was used to evaluate the suppression of flow-induced vibration interior noise in porous materials. The effects of flow velocity, thickness and density of the porous material, and three types of polyimide foam on the TL characteristics of the sandwich panel were investigated. The results show that the flow velocity has a significant influence on the TL of the sandwich panel. The TL of the sandwich panel decreases by 3–4 dB when the flow velocity increases by 100 km/h The B–A configuration has satisfactory sound insulation performance at most frequencies. With an increase in material thickness, the TL of the sandwich panel structure first increases and then decreases, and the material density mainly affects the TL of the structure at intermediate and high frequencies. Based on the objectives of maximizing the average transmission loss (TLavg) and minimizing the structural weight, the acoustic optimization design of the B–A structure was performed, and the balance between the two objective functions was achieved by a nondominated sorting genetic algorithm (NSGA-Ⅱ). The TLavg s of the sandwich panel structure increased by 5.2 dB when the total mass of the structure was decreased by 0.2 kg.
{"title":"Acoustic optimization design of porous materials on sandwich panel under flow-induced vibration","authors":"Ye Li, Xin-biao Xiao, Yumei Zhang, Zhao Tang, Aipeng Pan","doi":"10.1177/1475472X221150180","DOIUrl":"https://doi.org/10.1177/1475472X221150180","url":null,"abstract":"In this study, porous sound-absorbing materials used as a lining in double-panel structure applications (such as high-speed train body structures) to limit flow-induced vibration interior noise were studied, and acoustic optimization design was performed. First, in the wavenumber domain, the cross-spectrum Corcos model was used to characterize the dynamic hydrodynamic pressure of turbulence. Biot’s theory is used to model the porous materials. The transmission loss (TL) of the sandwich panel were also determined based on the model superposition method. Three types of sandwich panel structures were considered: air–air (A–A), bonded-bonded (B–B), and bonded-air (B–A). The TL of the three structure types under hydrodynamic pressure was used to evaluate the suppression of flow-induced vibration interior noise in porous materials. The effects of flow velocity, thickness and density of the porous material, and three types of polyimide foam on the TL characteristics of the sandwich panel were investigated. The results show that the flow velocity has a significant influence on the TL of the sandwich panel. The TL of the sandwich panel decreases by 3–4 dB when the flow velocity increases by 100 km/h The B–A configuration has satisfactory sound insulation performance at most frequencies. With an increase in material thickness, the TL of the sandwich panel structure first increases and then decreases, and the material density mainly affects the TL of the structure at intermediate and high frequencies. Based on the objectives of maximizing the average transmission loss (TLavg) and minimizing the structural weight, the acoustic optimization design of the B–A structure was performed, and the balance between the two objective functions was achieved by a nondominated sorting genetic algorithm (NSGA-Ⅱ). The TLavg s of the sandwich panel structure increased by 5.2 dB when the total mass of the structure was decreased by 0.2 kg.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44090898","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 : 2023-01-02DOI: 10.1177/1475472X221150175
Rong Xue, C. Mak, Dizi Wu, K. W. Ma
Helmholtz resonators (HR) are widely used in aero-engine systems for noise reduction. By connecting a pair of HRs in series (neck-cavity-neck-cavity), a dual HRs system is formed. This study investigated the influence of neck length, cavity volume and flow Mach number on the noise attenuation performance of a dual HRs system. A three-dimensional numerical simulation was performed to calculate the transmission loss results. The transmission loss (TL) results indicated that the second neck length can influence the second resonance frequency and TL max . Changing the cavity volume significantly influences the noise attenuation ability under lower flow rate conditions compared to higher flow rate conditions. The flow Mach number had a more significant impact on the first TL peak than on the second TL peak. This study shows the relationship between the geometric parameters, grazing flow and noise attenuation performance of a dual HRs system and could provide guidance in designing suitable dual HRs for aero-engine systems.
{"title":"The acoustic performance of a dual Helmholtz resonators system in the presence of a grazing flow","authors":"Rong Xue, C. Mak, Dizi Wu, K. W. Ma","doi":"10.1177/1475472X221150175","DOIUrl":"https://doi.org/10.1177/1475472X221150175","url":null,"abstract":"Helmholtz resonators (HR) are widely used in aero-engine systems for noise reduction. By connecting a pair of HRs in series (neck-cavity-neck-cavity), a dual HRs system is formed. This study investigated the influence of neck length, cavity volume and flow Mach number on the noise attenuation performance of a dual HRs system. A three-dimensional numerical simulation was performed to calculate the transmission loss results. The transmission loss (TL) results indicated that the second neck length can influence the second resonance frequency and TL max . Changing the cavity volume significantly influences the noise attenuation ability under lower flow rate conditions compared to higher flow rate conditions. The flow Mach number had a more significant impact on the first TL peak than on the second TL peak. This study shows the relationship between the geometric parameters, grazing flow and noise attenuation performance of a dual HRs system and could provide guidance in designing suitable dual HRs for aero-engine systems.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47326436","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 : 2023-01-02DOI: 10.1177/1475472X221150177
Yongle Du, Hangwen Yu, Yanchen Liu, Dangguo Yang
Development of advanced noise reduction devices requires an in-depth understanding of two fundamental questions: what are the true noise sources and how are the acoustic radiations generated. An accurate separation of the hydrodynamic and acoustic fluctuations helps to reveal the answers, but no consensus exists on its feasibility in the near-field source region of compressible flows. This study proposes a methodology to examine the dynamics of vortex sound generation in a two-dimensional artificially excited subsonic mixing layer. The parabolized stability equation (PSE) is applied to resolve the hydrodynamic fluctuations and the vortex sound theory is used to predict the acoustic pressures. Numerical simulations show that the PSE solutions capture the vortex pairing reasonably accurately and damp the acoustic modes to a negligible level, and that the vortex sound theory recovers the acoustic pressures. Good agreement of both solutions with the direct simulations indicates that a physically reasonable separation of hydrodynamic sources is achieved and can be used to further examine the vortex dynamics and noise source mechanisms.
{"title":"Hydrodynamic sources of the vortex sound in a two-dimensional shear layer","authors":"Yongle Du, Hangwen Yu, Yanchen Liu, Dangguo Yang","doi":"10.1177/1475472X221150177","DOIUrl":"https://doi.org/10.1177/1475472X221150177","url":null,"abstract":"Development of advanced noise reduction devices requires an in-depth understanding of two fundamental questions: what are the true noise sources and how are the acoustic radiations generated. An accurate separation of the hydrodynamic and acoustic fluctuations helps to reveal the answers, but no consensus exists on its feasibility in the near-field source region of compressible flows. This study proposes a methodology to examine the dynamics of vortex sound generation in a two-dimensional artificially excited subsonic mixing layer. The parabolized stability equation (PSE) is applied to resolve the hydrodynamic fluctuations and the vortex sound theory is used to predict the acoustic pressures. Numerical simulations show that the PSE solutions capture the vortex pairing reasonably accurately and damp the acoustic modes to a negligible level, and that the vortex sound theory recovers the acoustic pressures. Good agreement of both solutions with the direct simulations indicates that a physically reasonable separation of hydrodynamic sources is achieved and can be used to further examine the vortex dynamics and noise source mechanisms.","PeriodicalId":49304,"journal":{"name":"International Journal of Aeroacoustics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47879886","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}
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