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Pages: 209 - 209 Abstract: International Journal of Aeroacoustics, Volume 22, Issue 3-4, Page 209-209, June 2023.
Citation: International Journal of Aeroacoustics PubDate: 2023-07-10T04:02:24Z DOI: 10.1177/1475472X231183612 Issue No:Vol. 22, No. 3-4 (2023)
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Authors:Christopher KW Tam, John T Spyropoulos, Allan C Aubert, Russell W Powers Abstract: International Journal of Aeroacoustics, Ahead of Print. Ffowcs Williams et al were the first to discover crackle in the noise of the Concorde when the Olympus 593 engine which propelled Concorde was operating at afterburner power. Ffowcs Williams et al described crackle as a transient phenomenon. The primary objective of the present investigation is to show that the noise of F-18E aircraft has crackle. The fundamental elements in the noise of a crackling jet described by Ffowcs Williams et al are sawtooth-like pulses, bursts and trains of bursts. All these characteristic features of pressure pulses are identified in the noise of F-18E aircraft. By including a minimum pulse amplitude requirement based on the level found in the noise of the Concorde by Ffowcs Williams et al, a set of sufficiency conditions for the presence of crackle is established. It is found that crackle exists in the noise of an F-18E aircraft over a fairly large angular sector in the downstream direction. In the literature, the existence of sawtooth-like sound pulses in a noise field is often taken as an indicator of the presence of crackle. The importance of pressure pulse waveform on its impact on human hearing is briefly investigated by using a simple mechanical model of the ear. Citation: International Journal of Aeroacoustics PubDate: 2023-09-25T04:25:31Z DOI: 10.1177/1475472X231199182
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Authors:Jayanta Panda, Evan D Crowe, Lester A Langford, Earl T Daley, Kenneth R Hamm, Joel W Sills Abstract: International Journal of Aeroacoustics, Ahead of Print. A new phased array of microphones, suitable for the harsh environment of a rocket launch, was built and tested during a static firing of an RS-25 engine. It uses 70 piezo-resistive, dynamic pressure sensors, optimally distributed on a 10.5-ft diameter open frame dome structure and has a 200-ft long cable bundle to carry the signals to a weather-protected cabinet containing the data systems. The test stand was imaged using an infra-red camera and a visible wavelength camera, and the beamformed noise maps were superimposed on the photographs. The first-time data from a full-scale engine test stand showed that the plume deflector at the bottom of the engine was the primary noise source. The openings of the test stand around the nozzle exit were also found to be noise sources particularly at higher frequencies. The final goal is to utilize the array during NASA’s Artemis-II launch at Kennedy Space Center. Citation: International Journal of Aeroacoustics PubDate: 2023-09-15T12:00:17Z DOI: 10.1177/1475472X231199183
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Authors:Aharon Z. Karon, Krishan K. Ahuja Abstract: International Journal of Aeroacoustics, Ahead of Print. The Reynolds number and Mach number are classical quantities used to determine the similarity of aerodynamic flows. Existing studies on the role of Reynolds Number on jet noise show inconsistent results, casting doubt on how small a nozzle diameter can be for the classical jet noise scaling laws to hold. A systematic study was therefore undertaken to resolve this issue. The Reynolds number of jet flows was adjusted using a Mach number variation between 0.4 and 0.8, and nozzle-exit diameters of 0.25, 0.5, and two inches. When the jet noise measurements were normalized, spectral collapse was observed for the spectra across the whole Reynolds number range. It was found that the Reynolds number does not have a significant effect on jet noise, and jet noise can be scaled from even the smallest of nozzle to larger nozzles. Citation: International Journal of Aeroacoustics PubDate: 2023-09-07T05:12:29Z DOI: 10.1177/1475472X231199188
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Authors:Evren Yenigelen, Philip J Morris Abstract: International Journal of Aeroacoustics, Ahead of Print. The design of a rocket launch environment is a complex process with many different aspects that are highly interconnected. Acoustics, which is one of these, should be investigated in detail due to possible devastating effects on the launch vehicle, crew, and launch environment. This study uses a numerical method to consider a passive noise reduction method applied to a supersonic jet impinging on an inclined flame deflector to decrease the acoustic loads on the launch vehicle and noise levels in the far-field. In a supersonic jet impinging on an inclined flat plate configuration, acoustic waves that travel upstream originate from the impingement and wall jet regions. These upstream traveling waves are a combination of the acoustic waves that are produced by the high speed jet flows in the wall jet region and acoustic waves that reflect from the impingement wall. Due to the inclination of the impingement plate, these waves either travel to the far-field in the upstream direction or travel towards the free-jet region interacting with the high speed flow near the nozzle lip. This interaction can create a self sustaining feedback loop, which can cause acoustic tones to appear in the near- and far-field spectra. It is the aim of the present study to block the upstream traveling waves by introducing a second inclined wall with a circular cut-out between the nozzle exit and the impingement plate. Different configurations with different wall locations and cut-out sizes are investigated using a Detached Eddy Simulation CFD solver and an acoustic solver that is based on the Ffowcs Williams and Hawkings analogy. The mechanisms for the establishment of the feedback loops are examined. Citation: International Journal of Aeroacoustics PubDate: 2023-09-06T11:09:59Z DOI: 10.1177/1475472X231199184
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Authors:KBMQ Zaman Abstract: International Journal of Aeroacoustics, Ahead of Print. A set of 2-inch diameter nozzles is used to investigate the effect of varying exit boundary layer (BL) states on the radiated noise from high-subsonic jets. It is confirmed that nozzles involving turbulent boundary layers are the quietest while others, involving nominally-laminar BLs, are noisier. A turbulent BL is thicker and there is simply an effect of thickness on noise. A thicker BL results in a decrease in the sound pressure spectral amplitudes due to a less vigorous growth of instability waves in the jet’s shear layer. A nominally-laminar BL, besides being thinner, may also involve significantly higher turbulence intensities, much higher than that in a turbulent BL. Such a BL state, referred to as ‘highly disturbed laminar’, results in the largest noise amplitudes especially on the high-frequency side of the spectrum. This transitional state, often encountered with model scale nozzles, involves a ‘Blasius-like’ mean velocity profile but large velocity fluctuation intensities and intermittency. The higher initial turbulence adds to the increase in high-frequency noise. The results leave little doubt that an anomaly noted with subsonic jet noise databases in the literature is due to similar effects of differences in the initial boundary layer state. Citation: International Journal of Aeroacoustics PubDate: 2023-09-01T08:45:35Z DOI: 10.1177/1475472X231199189
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Authors:Robert P Dougherty Abstract: International Journal of Aeroacoustics, Ahead of Print. Prof. Krish Ahuja has a longstanding interest in jet noise source location. His work in this area is grounded in the idea that if the assumed source location is correct, then the sound should obey the inverse square law relative to that point and the phase should be constant along lines originating at that point. He applied this with, conceptually, one microphone in 1985 and two microphones in 1998. In 2006 he commissioned a beamforming system, Array 48, from OptiNav, Inc. His student, Nick Breen, used this to measure subsonic jet noise source location in detail. The NASA-Glenn Research Center also purchased an Array 48. In the current work, a jet noise data set measured by Gary Podboy using Glenn’s array in 2008 is revisited with a new beamforming algorithm, Robust Functional Beamforming, to further support Tam’s two-source model and Breen’s source location. Beamforming with modified steering vectors is performed to measure the parameters of the wavepacket source model from the far field. This process suggested replacing the wavepacket spatial length parameter with a temporal lifetime parameter. Another steering vector modification aimed to measure modes with odd spinning order. It seems to have found them at an apparent location 10 jet diameters removed from the jet, laterally. This is tentatively interpreted as a Mach radius phenomenon like one observed by Csaba Horvath at NASA-Glenn, also using Array 48, to study counter-rotating propeller noise. In an observation unrelated to beamforming, the excess noise measured at 40° from the jet axis as compared with the 90° angle, is fully contained in the first few cross spectral matrix eigenvalues, or Spectral Proper Orthogonal Decomposition modes, in some cases. Citation: International Journal of Aeroacoustics PubDate: 2023-08-26T02:24:26Z DOI: 10.1177/1475472X231199190
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Authors:Weicheng Bao, Xi Chen, Qijun Zhao, Dazhi Sun Abstract: International Journal of Aeroacoustics, Ahead of Print. In order to obtain the influence mechanism of the rotor noise and the local aerodynamic variation under different operating conditions, a novel discrete noise analysis strategy for the acoustic source localization is established. The analysis strategy has two aspects including the blade division method and the noise contribution calculation method. Firstly, the body-fitted rotor blade grids are preprocessed and refined at the division position before the flowfield simulation. Then, based on the flowfield result, the blade grids are divided into several blocks in the chordwise and spanwise directions, and the acoustic pressure of each block is predicted. Finally, a discriminant function for the contribution of the block to the rotor noise is proposed, and the acoustic source localization is carried out. The URANS equations and FW-H equations are used to capture high-fidelity flowfield and rotor acoustic pressure. Parameters such as the block position in different direction on the rotor blade and the collective pitches are quantified, and the relationship between air flow and aeroacoustics is discussed in detail. Some conclusions are obtained by analyzing the BO105 model rotor in hover. The acoustic pressure produced by the leading edge of the upper surface could cancel about 50% acoustic pressure of the remainder of these blocks. Increasing the force at this position will be benefit to the noise reduction. Acoustic source distribution is closely linked to the flow separation near the blade tip: the main acoustic source moves toward around 0.9 R section of the blade in the spanwise direction, and it moves from the leading edge towards the trailing edge in the chordwise direction. Citation: International Journal of Aeroacoustics PubDate: 2023-06-22T11:46:27Z DOI: 10.1177/1475472X231185068
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Authors:Ilker Goktepeli, Ulas Atmaca Abstract: International Journal of Aeroacoustics, Ahead of Print. Air flow characteristics of an open cavity have been numerically examined by using different turbulence models of Detached Eddy Simulation (DES), k-ε Realizable, k-ω Shear Stress Transport (SST) and Large Eddy Simulation (LES) based on an experimental study of open literature. Numerical results of transient analyses have been compared to experimental results at cavity length-based Reynolds number of Re = 4600. Pressure distributions, streamline patterns, streamwise velocity components, mean velocity values and their vectors have been given in terms of contour graphics. Moreover, velocity profiles have been presented. Pressure fluctuations have been triggered by flow separation and its reattachment. Due to upstream separation of boundary layer, there was curved boundary layer obtained between the outer potential-flow-like and the recirculation zones. As a result, negative velocity values are evidence for rotational flows affected by formation of secondary flows in the cavity. Furthermore, lower pressure region has been observed as a result of rotational flow which was powerful in the open cavity. Numerical results of DES and LES turbulence models are in good agreement with the results of reference study. As the numerical results obtained by LES turbulence model are approximately same with those of experimental reference study, LES turbulence model is mostly recommended. As an option to these turbulence models, k-ω SST model could be utilized for limited computer capacity. However, k-ε Realizable model is not sufficient for capturing rotational flows which are very effective in terms of present case. Citation: International Journal of Aeroacoustics PubDate: 2023-06-21T03:27:02Z DOI: 10.1177/1475472X231185082
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Authors:Wenyu Chen, Peng Wang, Yingzheng Liu Abstract: International Journal of Aeroacoustics, Ahead of Print. Acoustic wave scattering and fluid perturbations produced by interactions between incident acoustic wave and confined orifice flow were investigated by a combined numerical solution containing nonlinear flow simulation and linearized acoustic simulation. In flow simulations, the mainstream Reynolds number was fixed at 10,000, which relates to the cooling pipe system of lithography. Turbulent flow fields corresponding to different orifice geometries were solved by an opensource finite volume solver OpenFOAM with Reynolds-averaged Navier–Stokes turbulence model. The turbulence database could efficiently improve the accuracy of subsequent linearized acoustic simulations as the viscosity dissipations were considered. In acoustic simulations, the linearized Navier-Stokes equations were solved by a finite element solver with transformation into frequency domain. The incident acoustic waves with varying frequencies from 500 Hz to 4000 Hz were arranged first at the inlet and then the outlet surfaces, enabling a two-port analysis on the transmission and reflection coefficients of acoustic waves. The numerical setup and the two-port model were well validated by results in literature. Generally, acoustic waves tend to gradually dissipate as their frequencies increase or the opening ratio of the ducted orifice decreases. However, the nonlinear variation in the transmission and reflection coefficients against the frequency variation of the incident acoustic waves could be investigated by increasing the thickness ratio. The acoustically induced fluid perturbations that were characterized by the Q-criterion could form a ring shape vortex structure in the vicinity of the orifice edge and then develop into disk-like packets. When the circumferential shape of the orifice was changed to a square, the attenuation of the incident acoustic waves corresponded to the intensity of the three-dimensionality of the acoustic-induced vortex structures, which indicated a greater energy transfer from the acoustic waves to the fluid perturbations. Citation: International Journal of Aeroacoustics PubDate: 2023-06-15T01:13:44Z DOI: 10.1177/1475472X231183155
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Authors:Walter Eversman, Mary Drouin Abstract: International Journal of Aeroacoustics, Ahead of Print. Previously developed predictive models for impedance of single-degree-of-freedom and two-degree-of-freedom acoustic linings driven by a broad band acoustic source are reexamined. Two issues are addressed, the first being improvement of the conventional perforate face sheet impedance model. Data correlations based on flow bench measurements of steady flow pressure drop are reevaluated with emphasis on low flow velocity to improve the consistency of the prediction of linear resistance. In addition, for two-degree-of-freedom linings, face sheet mass reactance is modified to account for the presence of the septum. The second issue addresses the implication that for a non-linear lining, with impedance a function of the local sound pressure level, the installed performance of the lining depends on the local impedance, as opposed to impedance based on the source sound pressure level. This is investigated in the benchmarking of the impedance models by comparison of the acoustic transfer function predicted by a propagation code with the imbedded impedance model and transfer function measurements made in a grazing flow duct test facility. The propagation code is extended to make the non-linear behavior of the lining model dependent on the local acoustic spectrum, introducing an additional level of non-linearity and an iterative application of the propagation code. A principal conclusion is that with no grazing flow both the lining model and grazing flow duct transfer function measurements show a significant effect of local variation of the acoustic spectrum. With increasing grazing flow Mach number, this effect is reduced and effectively disappears at the highest Mach number. With increasing grazing flow Mach number the grazing flow contribution to face sheet resistance dominates and tends to mask the non-linear behavior of the component of resistance not related to grazing flow. Citation: International Journal of Aeroacoustics PubDate: 2023-06-14T02:50:46Z DOI: 10.1177/1475472X231183153
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Authors:Ayse Tiryakioglu, Burhan Tiryakioglu Abstract: International Journal of Aeroacoustics, Ahead of Print. In this study, the analysis of sound waves from a coaxial pipe with a perforated screen and a partial acoustic absorbing lining is investigated. The geometry under consideration consists of an infinite pipe placed in a semi-infinite cylindrical pipe such that the inner surface of the outer pipe is covered with a partial acoustic absorbing lining. Because of the partial lining, the solution is obtained with both the Jones’ method and the Mode-Matching method. The effects of the problem parameters such as perforated screen and partial lining on the radiation phenomenon are presented. Citation: International Journal of Aeroacoustics PubDate: 2023-06-12T10:28:26Z DOI: 10.1177/1475472X231183152
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Authors:Bingfei Liu, Yangjie Hao, Ping Chen Abstract: International Journal of Aeroacoustics, Ahead of Print. Due to the advantages of lightweight, small size, high stiffness, and adjustable parameters, plate metamaterials have shown great practical application value in the field of acoustic vibration control in engineering. For low-frequency vibration and noise control, an annular slotted bilayer plate metamaterial is designed, which can realize sound insulation and vibration reduction at 100–150 Hz (low-frequency range). By changing the geometric parameters of the annular slotted bilayer plate, the structural parameters of the additional mass, the material parameters, and its distribution position, the acting frequency band is reduced and the band gap of sound insulation and vibration reduction is widened. The integral metamaterial panels of circular and square PA12 were fabricated by 3D printing technology, and then, the acoustic and vibration characteristics were tested in the ZK1030 impedance tube system and Polytec full-field scanning laser vibration measurement system, respectively. The results show that the structure has the best performance by varying the resonant ring thickness of the lattice structure, controlling the wave incidence angle to 0°, and pointing force excitation in the X direction. However, when the mass of the additional mass block is certain, the distribution position of the mass block has less effect. The experimental result was reasonably consistent with the simulation analysis result. This work can provide a reference for the design of bilayer plate acoustic metamaterials with low-frequency broadband acoustic insulation and low-damping vibration based on periodic structures in engineering. Citation: International Journal of Aeroacoustics PubDate: 2023-06-10T01:24:21Z DOI: 10.1177/1475472X231183158
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Authors:Wenzhuo Zhang, Bingqian Li, Weiguo Yan, Zhen Wang, Xiaoqian Yang, Hongkun Li, Jianguo Chen, Jin Xu Abstract: International Journal of Aeroacoustics, Ahead of Print. Check valve is one of the core components of the scroll refrigeration compressor, which can directly affect its efficiency, life, and noise performance. Traditional check valve is the reed valve. This paper deeply studies the dynamic characteristics of reed valve and reveals the main reason of the valve noise under different rotation speeds. The large noise is mainly attributing to the large pressure pulsation as well as fast circulation velocity of fluid and the severe slapping of the reed plate on the valve seat, which is influenced by the high pressure ratio of the working condition and stiffness of the reed valve. In order to reduce the noise of the check valve, the circular valve is designed to replace reed valve in this paper. At each rotation speed, the circular valve shows a continuous exhaust process, which avoids the slapping of the valve plate on the valve seat. More importantly, the exhaust is smooth and the pressure pulsation as well as the flow rate of the fluid is reduced significantly leading to the low aerodynamic noise. Therefore, compared with the reed valve compressor, the sound pressure level of the circular valve compressor at 1800, 4200, and 6600 rpm is decreased by 3.0, 5.2, and 0.3 dB, respectively. Citation: International Journal of Aeroacoustics PubDate: 2023-06-10T01:16:21Z DOI: 10.1177/1475472X231183157
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Authors:Pieter Coenraad Swanepoel, Till M Biedermann, Sybrand J van der Spuy Abstract: International Journal of Aeroacoustics, Ahead of Print. Aerodynamic and aeroacoustic performance experiments were carried out on four- and eight bladed, 1.542 m diameter, axial flow cooling fans, with constant solidity and hub-to-tip ratio. Tests were conducted in an ISO5801, Type A Fan Test facility. The tip gap (TG) was reduced from 4 mm (0.26% fan diameter) to 2 mm (0.13% fan diameter), to 0 mm, for both fan configurations. The noise profile of each fan configuration at the same TG over the whole volumetric flow rate spectrum was compared to each other. The 4 mm (0.26%) TG is used as a baseline to measure the nett increase or decrease in sound levels. Noise emissions decreased as the TG was reduced. It is discovered that the four bladed fan configuration had lower noise emissions than the eight bladed fan configuration at all blade tip clearances at design flow rate. It is concluded that reducing the TG and number of blades, at constant solidity, reduces sound emissions. The 0 mm TG for the four bladed fan produced the greatest reduction in noise emissions. An increase in fan total-to-static performance is observed when reducing the TG for both fan configurations. Citation: International Journal of Aeroacoustics PubDate: 2023-06-08T08:42:13Z DOI: 10.1177/1475472X231183156
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Authors:Hasan Kamliya Jawahar, Stefano Meloni, Roberto Camussi Abstract: International Journal of Aeroacoustics, Ahead of Print. Imperfectly expanded jet flows are known to have additional noise sources known as Screech and broadband shock-associated noise. They are generated by the interaction between the instability waves that propagate from the lip of the nozzle and the shock cell structures. In this study, thorough experimental investigations were carried out on chevron nozzles to assess the importance of chevron parameters such as the chevron count and chevron penetration angle on the pressure field emitted by the jet. Data were acquired in the state-of-the-art aeroacoustic facility at the University of Bristol. Acoustic measurements such as pressure spectra, directivity and overall sound pressure levels along with near-field measurements were acquired for jet Mach numbers ranging from M = 1.1–1.4. Fourier-based and Wavelet-based analyses were used to highlight the different features of the various tested nozzles. Wavelet decomposition results highlight that the presence of the chevrons reduce the acoustic noise especially at a higher axial distance with increased levels of noise reduction achieved by chevron nozzle with deep penetration angle. Citation: International Journal of Aeroacoustics PubDate: 2022-06-21T06:18:18Z DOI: 10.1177/1475472X221101766
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Abstract: International Journal of Aeroacoustics, Ahead of Print.
Citation: International Journal of Aeroacoustics PubDate: 2022-04-12T03:00:03Z DOI: 10.1177/1475472X221096743
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