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1
Yang, Da, and Cheuk Ming Mak. "A combined sound field prediction method in small classrooms." Building Services Engineering Research and Technology 42, no. 4 (February 20, 2021): 375–88. http://dx.doi.org/10.1177/0143624421994229.
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In this paper, a new combination method for sound field prediction is proposed. An optimization approach based on the genetic algorithm is employed for optimizing the transition frequency of the combined sound field prediction method in classrooms. The selected optimization approach can identify the optimal transition frequency so that the combined sound field prediction can obtain more efficient and accurate prediction results. The proposed combined sound field prediction method consists of a wave-based method and geometric acoustic methods that are separated by the transition frequency. In low frequency domain (below the transition frequency), the sound field is calculated by the finite element method (FEM), while a hybrid geometric acoustic method is employed in the high frequency domain (above the transition frequency). The proposed combined prediction models are validated by comparing them with previous results and experimental measurements. The optimization approach is illustrated by several examples and compared with traditional combination results. Compared to existed sound field prediction simulations in classrooms, the proposed combination methods take the sound field in low frequencies into account. The results demonstrate the effectiveness of the proposed model. Practical applications: This study proposes a combined sound field prediction method separated by transition frequency. A genetic algorithm optimization method is employed for searching the optimal transition frequency. The outcomes of this paper are essential for acoustical designs and acoustical environmental assessments.
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Jierula, Alipujiang, Shuhong Wang, Tae-Min OH, and Pengyu Wang. "Study on Accuracy Metrics for Evaluating the Predictions of Damage Locations in Deep Piles Using Artificial Neural Networks with Acoustic Emission Data." Applied Sciences 11, no. 5 (March 5, 2021): 2314. http://dx.doi.org/10.3390/app11052314.
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Accuracy metrics have been widely used for the evaluation of predictions in machine learning. However, the selection of an appropriate accuracy metric for the evaluation of a specific prediction has not yet been specified. In this study, seven of the most used accuracy metrics in machine learning were summarized, and both their advantages and disadvantages were studied. To achieve this, the acoustic emission data of damage locations were collected from a pile hit test. A backpropagation artificial neural network prediction model for damage locations was trained with acoustic emission data using six different training algorithms, and the prediction accuracies of six algorithms were evaluated using seven different accuracy metrics. Test results showed that the training algorithm of “TRAINGLM” exhibited the best performance for predicting damage locations in deep piles. Subsequently, the artificial neural networks were trained using three different datasets collected from three acoustic emission sensor groups, and the prediction accuracies of three models were evaluated with the seven different accuracy metrics. The test results showed that the dataset collected from the pile body-installed sensors group exhibited the highest accuracy for predicting damage locations in deep piles. Subsequently, the correlations between the seven accuracy metrics and the sensitivity of each accuracy metrics were discussed based on the analysis results. Eventually, a novel selection method for an appropriate accuracy metric to evaluate the accuracy of specific predictions was proposed. This novel method is useful to select an appropriate accuracy metric for wide predictions, especially in the engineering field.
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Semiletov, Vasily A., and Sergey A. Karabasov. "Similarity scaling of jet noise sources for low-order jet noise modelling based on the Goldstein generalised acoustic analogy." International Journal of Aeroacoustics 16, no. 6 (September 2017): 476–90. http://dx.doi.org/10.1177/1475472x17730457.
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As a first step towards a robust low-order modelling framework that is free from either calibration parameters based on the far-field noise data or any assumptions about the noise source structure, a new low-order noise prediction scheme is implemented. The scheme is based on the Goldstein generalised acoustic analogy and uses the Large Eddy Simulation database of fluctuating Reynolds stress fields from the CABARET MILES solution of Semiletov et al. corresponding to a static isothermal jet from the SILOET experiment for reconstruction of effective noise sources. The sources are scaled in accordance with the physics-based arguments and the corresponding sound meanflow propagation problem is solved using a frequency domain Green’s function method for each jet case. Results of the far-field noise predictions of the new method are validated for the two NASA SHJAR jet cases, sp07 and sp03 from and compared with the reference predictions, which are obtained by applying the Lighthill acoustic analogy scaling for the SILOET far-field measurements and using an empirical jet-noise prediction code, sJet.
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Miller, SAE, and Alexander N. Carr. "Theoretical investigation of alteration and radiation of large-scale structures due to jet impingement." International Journal of Aeroacoustics 18, no. 2-3 (December 20, 2018): 231–57. http://dx.doi.org/10.1177/1475472x18812810.
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Jet flows impinge on launch pad structures and aircraft carrier deck blast deflectors. Turbulent structures are deformed and acoustic radiation is reflected by the deflector. The coupling of reflected acoustic waves with the instability waves of the jet turbulence increases their amplitude and causes a feedback loop. Resultant far-field acoustic radiation is amplified. This amplification results in additional tones with significant spectral broadening occurring at frequencies corresponding to the constructive interference. We present a simple prediction methodology in the form of an acoustic analogy. The analogy accounts for reflected acoustic waves through a tailored Green’s function and models the large-scale structures as spatially and temporarily growing and decaying instability waves. The predictions are compared with two experimental datasets. Predictions compare favorably with measured frequencies and spectral broadening in the far-field.
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Zhong, Siyang, and Xin Zhang. "A sound extrapolation method for aeroacoustics far-field prediction in presence of vortical waves." Journal of Fluid Mechanics 820 (May 8, 2017): 424–50. http://dx.doi.org/10.1017/jfm.2017.219.
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Off-surface integral solutions to an inhomogeneous wave equation based on acoustic analogy could suffer from spurious wave contamination when volume integrals are ignored for computation efficiency and vortical/turbulent gusts are convected across the integration surfaces, leading to erroneous far-field directivity predictions. Vortical gusts often exist in aerodynamic flows and it is inevitable their effects are present on the integration surface. In this work, we propose a new sound extrapolation method for acoustic far-field directivity prediction in the presence of vortical gusts, which overcomes the deficiencies in the existing methods. The Euler equations are rearranged to an alternative form in terms of fluctuation variables that contains the possible acoustical and vortical waves. Then the equations are manipulated to an inhomogeneous wave equation with source terms corresponding to surface and volume integrals. With the new formulation, spurious monopole and dipole noise produced by vortical gusts can be suppressed on account of the solenoidal property of the vortical waves and a simple convection process. It is therefore valid to ignore the volume integrals and preserve the sound properties. The resulting new acoustic inhomogeneous convected wave equations could be solved by means of the Green’s function method. Validation and verification cases are investigated, and the proposed method shows a capacity of accurate sound prediction for these cases. The new method is also applied to the challenging airfoil leading edge noise problems by injecting vortical waves into the computational domain and performing aeroacoustic studies at both subsonic and transonic speeds. In the case of a transonic airfoil leading edge noise problem, shocks are present on the airfoil surface. Good agreements of the directivity patterns are obtained compared with direct computation results.
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Salin, M. B., and D. A. Kosteev. "Nearfield acoustic holography-based methods for far field prediction." Applied Acoustics 159 (February 2020): 107099. http://dx.doi.org/10.1016/j.apacoust.2019.107099.
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Gao, Sheng Yao, and De Shi Wang. "An Indirect Boundary Element Method for Computing Sound Field." Advanced Materials Research 476-478 (February 2012): 1173–77. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.1173.
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Computing sound field from an arbitrary radiator is of interest in acoustics, with many significant applications, one that includes the design of classical projectors and the noise prediction of underwater vehicle. To overcome the non-uniqueness of solution at eigenfrequencies in the boundary integral equation method for structural acoustic radiation, wave superposition method is introduced to study the acoustics. In this paper, the theoretical backgrounds to the direct boundary element method and the wave superposition method are presented. The wave superposition method does not solve the Kirchoff-Helmholtz integral equation directly. In the approach a lumped parameter model is estabiled from spatially averaged quantities, and the numerical method is implemented by using the acoustic field from a series of virtual sources which are collocated near the boundary surface to replace the acoustic field of the radiator. Then the sound field over the of a pulsating sphere is calculated. Finally, comparison between the analytical and numerical results is given, and the speed of solution is investigated. The results show that the agreement between the results from the above numerical methods is excellent. The wave superposition method requires fewer elements and hence is faster, which do not need as high a mesh density as traditionally associated with BEM.
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Tao, Jun, Gang Sun, Ying Hu, and Miao Zhang. "Noise Prediction for Multi-Element Airfoil Based on FW-H Equation." Applied Mechanics and Materials 52-54 (March 2011): 1388–93. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.1388.
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In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.
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Lebon, Bruno, Iakovos Tzanakis, Koulis Pericleous, and Dmitry Eskin. "Numerical Modelling of the Ultrasonic Treatment of Aluminium Melts: An Overview of Recent Advances." Materials 12, no. 19 (October 6, 2019): 3262. http://dx.doi.org/10.3390/ma12193262.
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The prediction of the acoustic pressure field and associated streaming is of paramount importance to ultrasonic melt processing. Hence, the last decade has witnessed the emergence of various numerical models for predicting acoustic pressures and velocity fields in liquid metals subject to ultrasonic excitation at large amplitudes. This paper summarizes recent research, arguably the state of the art, and suggests best practice guidelines in acoustic cavitation modelling as applied to aluminium melts. We also present the remaining challenges that are to be addressed to pave the way for a reliable and complete working numerical package that can assist in scaling up this promising technology.
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de Souza, Mauricy Cesar R., and Samir N. Y. Gerges. "Prediction of Sound Level in Rooms and Experimental Validation." Building Acoustics 4, no. 2 (June 1997): 117–35. http://dx.doi.org/10.1177/1351010x9700400204.
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Traditional Sabine equations still are used for factories or offices where diffuse sound fields rarely occur and prediction can be inaccurate. More recently, methods based on geometric acoustics have been developed which require large computing time and which demand better defined input data. A problem, often encountered, is how to include input data which is appropriate, accurate and relatively easy to obtain. Three acoustic models of a furnished room were created: a diffuse field, an image source and a ray tracing model. The initial values of absorption coefficient and sound power level were obtained by standard measurements and the sound propagation SP was predicted and compared with measurement for each model. Then, the models were calibrated by altering the input parameters in order to minimise the difference between predicted and measured values. Sound pressure level due to two sources was also predicted and compared with measurement. For the room studied, the precision of the predictions, after calibration, is similar for the three models considered, with an average difference between simulated and measured values of less than 2 dB. Without the calibration procedure, the ray-tracing model gave the most precise first estimate. The diffuse and image source models needed significant modification of the input data to obtain a similar precision. The sound field in the room chosen for this study was nearly diffuse and simulation, based on geometric acoustics, did not offer clear advantages. However, this will not be the case for rooms with more complicated geometrical and acoustic characteristics such as in factories and offices. In addition, the image source model will not be appropriate for internal fittings which are much more complex than in the present study and an appropriate estimate of the scattering cross-section is problematical. In the ray tracing model, this problem is circumvented by incorporating the fittings as part of the geometry of the room.
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Estrada, Héctor, Johannes Rebling, and Daniel Razansky. "Prediction and near-field observation of skull-guided acoustic waves." Physics in Medicine and Biology 62, no. 12 (May 16, 2017): 4728–40. http://dx.doi.org/10.1088/1361-6560/aa63e3.
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Laborde, J. L., C. Bouyer, J. P. Caltagirone, and A. Gérard. "Acoustic cavitation field prediction at low and high frequency ultrasounds." Ultrasonics 36, no. 1-5 (February 1998): 581–87. http://dx.doi.org/10.1016/s0041-624x(97)00106-6.
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Zheng, Zhengyu. "Prediction of dipole sources and aeroacoustics field for tandem cylinder flow field based on DBEM/hybrid LES." International Journal of Aeroacoustics 20, no. 1-2 (January 10, 2021): 157–73. http://dx.doi.org/10.1177/1475472x20984092.
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In this paper, the DBEM/Hybrid LES（Directly Boundary Element Method/Hybrid Large Eddy Simulation）technique is applied to predict the aerodynamic noise generated by tandem circular cylinders immersed in a three-dimensional turbulent flow. Utilizing the Lighthill's Acoustic Analogy, the flow pressure fluctuation near the surface of the cylinder is converted into acoustic dipole sources. Taking the dipole sound sources as the actual sound sources, the aeroacoustic field is simulated and analyzed by DBEM. The research shows that: The strong dipole sources are distributed in the collision zone of the downstream cylindrical surface, where the upstream cylinder's shedding vortex colliding to downstream cylinder surface. Both of the amplitude-frequency response and the phase-frequency response of dipole acoustic source are obtained, which is helpful for further research on aerodynamics noise interference and suppression. Good comparisons are obtained between numerical results and BART (Basic Aerodynamic Research Tunnel) experimental data published by NASA.
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Stewart, James D., Ross Koppenaal, Antoine Lalumière, and Roger J. Whitehead. "Predicting wood stiffness of lodgepole pine trees using acoustic tools and green density." Forestry Chronicle 97, no. 01 (January 2021): 52–64. http://dx.doi.org/10.5558/tfc2021-007.
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Upstream identification of wood properties using non-destructive testing methods such as acoustic velocity (AV) measurements is important for optimizing allocation of wood to mills or products. We evaluated the effectiveness of field AV measurement tools in predicting lodgepole pine wood stiffness (modulus of elasticity, MOE) as measured by Silviscan on wood samples. AV was measured on trees and logs from six sites in Alberta and British Columbia. We evaluated the effect on MOE estimation of calculating averages of the adjustment factor k and of green density (GD) at different spatial scales from individual tree to population. The effect of using forest inventory variables on MOE prediction were also examined. Prediction of tree-level MOE from tree-level measurements of AV, k and GD resulted in R2 values of 0.59. Using estimates of k and GD averaged at plot, site or population scales significantly diminished the R2 of the MOE predictions at tree level. Predicting MOE at plot or stand level from corresponding averages of AV, k and GD gave R2 values >0.8. Including inventory variables in tree-level MOE predictions increased the R2 to 0.62. AV measurements can give operationally useful estimates of MOE in lodgepole pine trees at the stand level.
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Chen, Ning, Dejie Yu, Baizhan Xia, and Michael Beer. "Hybrid Uncertain Analysis for Exterior Acoustic Field Prediction with Interval Random Parameters." International Journal of Computational Methods 15, no. 02 (September 28, 2017): 1850006. http://dx.doi.org/10.1142/s0219876218500068.
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For exterior acoustic field problems that lack sufficient information to construct precise probability distributions, an interval random model is introduced to deal with the uncertain parameters. In the interval random model, the probability variables are employed to treat the uncertain parameters, whereas some distribution parameters of random variables are modeled as interval variables instead of precise values. Based on the interval random model, the interval random finite element equation for exterior acoustic fields is established and a hybrid uncertain analysis method is presented to solve the exterior acoustic field problem with interval random variables. In the presented method, by temporarily neglecting the uncertainties of interval variables, a first-order stochastic perturbation method is adopted to calculate the expectation and the variance of the response vector. According to the monotonicity of the expectation and variance of the response vector with respect to the interval variables, the lower and upper bounds of the expectation and variance of the response vector can be calculated by the vertex method. In addition, in order to ensure accuracy of the proposed method, the subinterval technique is introduced and investigated. The numerical example of a square flexible shell model is presented to demonstrate the effectiveness of the proposed method.
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Dong, Qichao, Xintian Liu, Hongzhong Qi, and Yafu Zhou. "Vibro-acoustic prediction and evaluation of permanent magnet synchronous motors." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 12 (June 9, 2020): 2783–93. http://dx.doi.org/10.1177/0954407020919659.
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In this study, a multiphysics finite element method is proposed to predict and evaluate the electromagnetic vibration and noise of the permanent magnet synchronous motors. First, the expressions of radial electromagnetic force waves were derived based on the established mathematical models of airgap magnetic field using the analytical methods. Subsequently, the main circumferential spatial orders influencing electromagnetic noise were analyzed and discussed. Then, a multiphysics simulation model that consists of mechanical field, electromagnetic field, and acoustic field was established for the calculation of the electromagnetic radiation noise. Finally, the multiphysics simulation model developed for the electromagnetic vibration and noise prediction was validated by comparing the finite element analysis and experimental data. It is shown that, although the local differences exist, the results from the finite element calculation and test analysis have a good agreement on the analytical mechanism overall, both in amplitude and main orders. In addition, this paper has made a detailed analysis to the electromagnetic noise generation mechanism, which lays the basis for further study in predicting and suppressing the electromagnetic vibration and noise of the drive motors of pure electric vehicle.
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Liu, Jinpeng, Zheng Zhu, Yongqiang Ji, Ziyang Chen, Chao Zhang, and Dejiang Shang. "Prediction of Sound Scattering from Deep-Sea Targets Based on Equivalence of Directional Point Sources." Applied Sciences 11, no. 11 (June 2, 2021): 5160. http://dx.doi.org/10.3390/app11115160.
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A fast prediction method is proposed for calculating the sound scattering of targets in the deep-sea acoustic channel by equating the sound scattering field of a complex elastic target to the acoustic field excited by a directional point source. In deep-sea conditions, the effects of the sea surface on the impedance characteristics of the elastic target surface can be ignored. Through the finite element simulation of the acoustic scattering of the target in the free field, the sound scattering field is equated to the radiation field of a directional point source. Subsequently, the point source is placed in the channel, and the acoustic ray method is used to calculate the distribution of the scattering field. On the basis of theoretical modelling, the method of obtaining the directional point source and the influence of the sea surface on the impedance of the scattering field are analysed. Subsequently, the proposed method is compared with the finite element method in terms of computational efficiency. The result shows that the method considers the multiple complex coupling effects between the elastic structure and marine environment. The influence of the boundary is approximately negligible when the distance from the ocean boundary to the elastic structure is equal to the wavelength. The method only performs finite element coupling calculation in the free field; the amount of mesh size is greatly reduced and the calculation efficiency is significantly improved when compared with the finite element calculation in the entire channel, the. The calculation time in the example can be reduced by more than one order of magnitude. This method organically combines the near-field calculation with acoustic ray theory and it can realise the rapid calculation of the large-scale acoustic scattering field in complex marine environments.
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Férand, Mélissa, Thomas Livebardon, Stéphane Moreau, and Marlène Sanjosé. "Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines." Acoustics 1, no. 1 (February 19, 2019): 174–98. http://dx.doi.org/10.3390/acoustics1010012.
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A hybrid methodology combining a detailed Large Eddy Simulation of a combustion chamber sector, an analytical propagation model of the extracted acoustic and entropy waves at the combustor exit through the turbine stages, and a far-field acoustic propagation through a variable exhaust temperature field was shown to predict far-field combustion noise from helicopter and aircraft propulsion systems accurately for the first time. For the single-stream turboshaft engine, the validation was achieved from engine core to the turbine exit. Propagation to the far field was then performed through a modeled axisymmetric jet. Its temperature modified the acoustic propagation of combustion noise significantly and a simple analytical model based on the Snell–Descarte law was shown to predict the directivity for axisymmetric single jet exhaust accurately. Good agreement with measured far-field spectra for all turboshaft-engine regimes below 2 kHz stresses that combustion noise is most likely the dominant noise source at low frequencies in such engines. For the more complex dual-stream turbofan engine, two regime computations showed that direct noise is mostly generated by the unsteady flame dynamics and the indirect combustion noise by the temperature stratification induced by the dilution holes in the combustion chamber, as found previously in the turboshaft case. However, in the turboengine, direct noise was found dominant at the combustor exit for the low power case and equivalent contributions of both combustion noise sources for the high power case. The propagation to the far-field was achieved through the temperature field provided by a Reynolds-Averaged Navier–Stokes simulation. Good agreement with measured spectra was also found at low frequencies for the low power turboengine case. At high power, however, turboengine jet noise overcomes combustion noise at low frequencies.
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Fleig, Oliver, Makoto Iida, and Chuichi Arakawa. "Wind Turbine Blade Tip Flow and Noise Prediction by Large-eddy Simulation." Journal of Solar Energy Engineering 126, no. 4 (November 1, 2004): 1017–24. http://dx.doi.org/10.1115/1.1800551.
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The purpose of this research is to investigate the physical mechanisms associated with broadband tip vortex noise caused by rotating wind turbines. The flow and acoustic field around a wind turbine blade is simulated using compressible large-eddy simulation and direct noise simulation, with emphasis on the blade tip region. The far field aerodynamic noise is modeled using acoustic analogy. Aerodynamic performance and acoustic emissions are predicted for the actual tip shape and an ogee type tip shape. For the ogee type tip shape the sound pressure level decreases by 5 dB for frequencies above 4 kHz.
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Yu, Chao, Zhengfang Zhou, Mei Zhuang, Xiaodong Li, and Frank Thiele. "Effective Far-Field Acoustic Prediction Method and Its Computational Aeroacoustics Applications." AIAA Journal 47, no. 2 (February 2009): 410–17. http://dx.doi.org/10.2514/1.39009.
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Zhou, Ji‐Xun, Xue‐Zhen Zhang, Peter H. Rogers, and Gary W. Caille. "Average acoustic field in shallow water I: Active sonar performance prediction." Journal of the Acoustical Society of America 96, no. 5 (November 1994): 3330. http://dx.doi.org/10.1121/1.410747.
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Zhong, Siyang, Xin Zhang, and Xun Huang. "A comparison of acoustic far-field prediction methods for turbulent flows." International Journal of Aeroacoustics 18, no. 6-7 (October 2019): 579–95. http://dx.doi.org/10.1177/1475472x19871525.
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Xia, Tiejian, Yuebing Wang, Lisheng Zhou, and Qiang Liu. "Prediction for the acoustic field of a high frequency cylindrical transducer." Journal of the Acoustical Society of America 123, no. 5 (May 2008): 3437. http://dx.doi.org/10.1121/1.2934228.
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Wang, Shiquan. "Far-Field Performances Prediction of High Frequency Projectors Using Secondary Source Array Method." Journal of Computational Acoustics 25, no. 02 (November 2, 2016): 1750002. http://dx.doi.org/10.1142/s0218396x17500023.
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This paper investigates the prediction of the far-field performances of high frequency projectors using the second source array method (SSAM). The far-field parameters can be calculated accurately using the complex acoustic pressure data of two very close parallel planes which lie in the near-field region of the projector. The paper simulates the feasibility of predicting the far-field parameters such as transmitting voltage response and the far-field directivity pattern. The predicting results are compared with that calculated using boundary element method (BEM). It shows very good agreement between the two methods. A planar high frequency projector is measured using the near-field method. In order to verify the predicting results, the far-field measurement is performed for the same projector. The comparison of the results shows that the near-field method is capable to precisely predict the far-field parameters of the projector.
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Han, Gang, Keith Shepstone, Iwan Harmawan, Ufuk Er, Hasni Jusoh, Lim Sue Lin, Dave Pringle, et al. "A Comprehensive Study of Sanding Rate From a Gas Field: From Reservoir to Completion, Production, and Surface Facilities." SPE Journal 16, no. 02 (January 13, 2011): 463–81. http://dx.doi.org/10.2118/123478-pa.
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Summary An offshore gas field has been producing sand for a few years. Sand production has been closely monitored through acoustic flowline devices and a sand-collection system installed on the platforms. Observation of sand production has triggered evaluation of whether to install surface desanders or to complete future wells with downhole sand control. This evaluation requires a prediction of sanding rate over the reservoir life. The possibility of providing downhole sand control on existing wells was also evaluated in separate studies. Predicting sanding rate, particularly for gas fields, has been historically challenging, mainly because of the sporadic nature of sand production, inadequate quantification of fundamental physics, and lack of representative laboratory tests and reliable field calibration. To tackle these challenges, four studies have been designed and executed: (1) the development of a reliable log-based rock-strength estimate, (2) the prediction of sanding rate over the reservoir life for a conservative well condition, (3) the evaluation of sand-particle transport from the reservoir to the surface facilities, and (4) the estimate of potential erosion of platform facilities. The sanding-rate prediction is based on extensive laboratory tests of four carefully selected whole cores with gas and water flow. It then has been validated by field-monitoring data from an acoustic flowline device on each producer and a sand-collection system on the platforms. The studies have provided a prediction of (1) future sand production, (2) how much of the produced sand will be seen at the surface (and, therefore, how much of it will fall into the rathole), (3) how fast various components of the surface facility will erode over the field life, and (4) what will be the optimal completion strategy for sand control should it become necessary. They have provided input to an integrated evaluation of completion design, reservoir management, platform configuration, and field economics.
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Hu, Binfei, Zengjun Lu, Qiming Cui, Rongjiang Tang, Zhe Feng, and Daokun Bi. "Prediction and Aerodynamic Analysis of Interior Noise and Wind Drag Generated by the Outside Rear-View Mirror for Commercial Vehicles." Shock and Vibration 2020 (September 14, 2020): 1–16. http://dx.doi.org/10.1155/2020/8893959.
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The outside rear-view mirror (OSRVM) is installed on the vehicle’s surface, which causes unwanted aerodynamic noise and wind drag during driving. It is important to use simulation methods to predict the performance of aerodynamic noise and wind drag of commercial vehicles due to the OSRVM. Considering the wind drag of the OSRVM, a combinational simulation strategy is employed to calculate external flow and interior acoustic fields of commercial vehicles, respectively. The flow field is computed a priori with an incompressible flow solver. The acoustic field was then computed based on the information extracted from the CFD solver. To obtain the interior noise level at the driver’s ears, a vibroacoustic model is used to calculate the response of the window glass structure and interior cavities, where the unsteady aerodynamic pressure loading on the two side windows’ surface is treated as the acoustic source field. The paper provides flow field and acoustic simulations for three OSRVM configuration models. The results are compared to data obtained in road sliding test measurement on the commercial vehicle. The accuracy of the hybrid simulation method is proved, and the comparative analyses verify that the OSRVM B model dramatically reduces the interior noise and wind drag of commercial vehicles.
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Wang, Wenbo, Desen Yang, and Jie Shi. "A Prediction Method for Acoustic Intensity Vector Field of Elastic Structure in Shallow Water Waveguide." Shock and Vibration 2020 (October 17, 2020): 1–23. http://dx.doi.org/10.1155/2020/5389719.
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Compared with scalar sound field, vector sound field explained the spatial structure of sound field better since it not only presents the sound energy distribution but also describes the sound energy flow characteristics. Particularly, with more complicated interaction among different wavefronts, the vector sound field characteristics of an elastic structure in a shallow water waveguide are worthy of studying. However, there is no reliable prediction method for the vector sound field of an elastic structure with a high efficiency in a shallow water waveguide. To solve the problem, transfer functions in the waveguide have been modified with some approximations to apply for the vector sound field prediction of elastic structures in shallow water waveguides. The method is based on the combined wave superposition method (CWSM), which has been proved to be efficient for predicting scalar sound field. The rationality of the approximations is validated with simulations. Characteristics of the complex acoustic intensity, especially the vertical components are observed. The results show that, with constructive and destructive interferences in the depth direction, there could be quantities of crests and vortices in the spatial structure of time-dependent complex intensity, which manifest a unique dynamic characteristic of sound energy. With more complicated interactions among the wavefronts, a structure source could not be equivalent to a point source in most instances. The vector sound field characteristics of the two sources could be entirely different, even though the scalar sound field characteristics are similar. Meanwhile, source types, source parameters, ocean environment parameters, and geo parameters may have influence on the vector sound field characteristics, which could be explained with the normal mode theory.
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Cho, Yong Thung, J. Stuart Bolton, and Michael J. Roan. "Acoustic source property prediction based on near-field measurements in planar coordinate." Journal of Sound and Vibration 324, no. 3-5 (July 2009): 587–607. http://dx.doi.org/10.1016/j.jsv.2009.02.033.
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Bernardini, Giovanni, Jacopo Serafini, Sandro Lanniello, and Massimo Gennaretti. "Assessment of Computational Models for the Effect of Aeroelasticity on BVI Noise Prediction." International Journal of Aeroacoustics 6, no. 3 (September 2007): 199–222. http://dx.doi.org/10.1260/147547207782419570.
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This paper deals with the computational analysis of acoustic fields generated by helicopter rotors when Blade-Vortex Interactions (BVI) occur. The prediction procedure starts from the determination of the steady periodic blade deformations. Then, the BVI-affected, unsteady aerodynamics solution is obtained by a potential-flow boundary integral formulation suited for aeronautical configurations experiencing blade-wake impingements. It is applicable to blades with arbitrary shape and motion and evaluates both wake distortion and blade pressure field. Finally, the noise field radiated by the rotor is computed through an aeroacoustic tool based on the Ffowcs Williams and Hawkings equation. The numerical investigation examines the sensitivity of BVI noise prediction on the aeroelastic model applied for the calculation of blade deformations, and assesses the accuracy of the results through correlation with experimental data concerning a helicopter main rotor in descent flight. Noise predicted is examined in terms of both acoustic pressure signatures and noise radiation characteristics.
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Bi, Chuanxing. "RECONSTRUCTION AND PREDICTION OF ACOUSTIC FIELD IN THE DISTRIBUTED SOURCE BOUNDARY POINT METHOD BASED NEARFIELD ACOUSTIC HOLOGRAPHY." Chinese Journal of Mechanical Engineering 39, no. 08 (2003): 81. http://dx.doi.org/10.3901/jme.2003.08.081.
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Huang, Hongpu, Zhenlin Ji, and Kangjian Han. "Acoustic Behavior Prediction and Analysis of Resonators in the Presence of Low Mach Number Flow." Journal of Theoretical and Computational Acoustics 28, no. 03 (January 7, 2020): 1950015. http://dx.doi.org/10.1142/s2591728519500154.
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The frequency-domain linearized Navier–Stokes equations (LNSEs) are used to describe the sound field of Helmholtz resonators and concentric perforated tube resonators in the presence of low Mach number flow. The numerical procedure of LNSEs method is performed in three steps, computational fluid dynamics (CFD) calculation, data transfer and acoustics calculation. The transmission loss predictions of the resonators exhibit good agreement with measurements published in the literature. The results show that the low Mach number flow shifts the resonance frequencies of resonators and changes the acoustic attenuation behavior, which may be attributed to the change of acoustic impedance of the opening and orifices. In order to weaken the effect of flow on the resonance frequency, the modified configurations of resonators are proposed by using the conical tubes to reduce the flow velocity passing the opening and orifices. Numerical results demonstrated that the influence of flow velocity on the resonance frequency of the modified resonators is less sensitive than the original configurations.
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SANDBERG, RICHARD D., and NEIL D. SANDHAM. "Direct numerical simulation of turbulent flow past a trailing edge and the associated noise generation." Journal of Fluid Mechanics 596 (January 17, 2008): 353–85. http://dx.doi.org/10.1017/s0022112007009561.
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Direct numerical simulations (DNS) are conducted of turbulent flow passing an infinitely thin trailing edge. The objective is to investigate the turbulent flow field in the vicinity of the trailing edge and the associated broadband noise generation. To generate a turbulent boundary layer a short distance from the inflow boundary, high-amplitude lifted streaks and disturbances that can be associated with coherent outer-layer vortices are introduced at the inflow boundary. A rapid increase in skin friction and a decrease in boundary layer thickness and pressure fluctuations is observed at the trailing edge. It is demonstrated that the behaviour of the hydrodynamic field in the vicinity of the trailing edge can be predicted with reasonable accuracy using triple-deck theory if the eddy viscosity is accounted for. Point spectra of surface pressure difference are shown to vary considerably towards the trailing edge, with a significant reduction of amplitude occurring in the low-frequency range. The acoustic pressure obtained from the DNS is compared with predictions from two- and three-dimensional acoustic analogies and the classical trailing-edge theory of Amiet. For low frequencies, two-dimensional theory succeeds in predicting the acoustic pressure in the far field with reasonable accuracy due to a significant spanwise coherence of the surface pressure difference and predominantly two-dimensional sound radiation. For higher frequencies, however, the full three-dimensional theory is required for an accurate prediction of the acoustic far field. DNS data are used to test some of the key assumptions invoked by Amiet for the derivation of the classical trailing-edge theory. Even though most of the approximations are shown to be reasonable, they collectively lead to a deviation from the DNS results, in particular for higher frequencies. Moreover, because the three-dimensional acoustic analogy does not provide significantly improved results, it is suggested that some of the discrepancies can be attributed to the approach of evaluating the far-field sound using a Kirchhoff-type integration of the surface pressure difference.
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Sujith, R. I., G. A. Waldherr, J. I. Jagoda, and B. T. Zinn. "An Experimental Investigation of the Behavior of Droplets in Axial Acoustic Fields." Journal of Vibration and Acoustics 119, no. 3 (July 1, 1997): 285–92. http://dx.doi.org/10.1115/1.2889722.
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This paper describes an experimental investigation of the behavior of water droplets in axial acoustic fields. It was motivated by the increasing interest in the use of pulsations to improve the performance of energy intensive, industrial processes. The presence of an acoustic field is believed to enhance heat and mass transfer to and from the droplets, probably because of the relative motion between the droplets and the gas phase. This relative motion is characterized by the ratio of the amplitude of the oscillatory droplet velocity to that of the acoustic velocity (entrainment factor), and by the phase between the droplet and gas phase oscillations. An experimental set-up was developed to investigate the effect of acoustic oscillations on the motion of individual droplets. In these experiments a droplet produced by a piezo-ceramic droplet generator is allowed to fall through a transparent test section in which an acoustic field has been set up using a pair of acoustic drivers. Images of the droplets in the test section acquired at consecutive instants using a high speed, intensified imaging system were used to determine the time dependent droplet trajectory and velocity. The acoustic velocity was calculated from measured acoustic pressure distributions. The entrainment factor and the phase difference were then determined from these data. The results show how the entrainment factor decreases and the phase difference increases with increasing droplet diameter and frequency, indicating that larger diameters and higher frequencies reduce the “ability” of the droplets to follow the gas phase oscillations. The measured data are in excellent agreement with the prediction of the Hjelmfelt and Mockros model. Both theoretical predictions and measured data were correlated with the Stokes number, which accounts for the effects of droplet diameter and frequency. It was also shown that acoustic oscillations decrease the mean terminal velocity of the droplets.
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Zhou, Shuiqing, and Jun Wang. "Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan." Advances in Mechanical Engineering 6 (January 1, 2014): 712421. http://dx.doi.org/10.1155/2014/712421.
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An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.
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Qin, Qikai, Dejiang Shang, Yongwei Liu, and Tianyu Wang. "Prediction of flow noise around a cylinder based on Large-Eddy Simulation and acoustic analogy method." MATEC Web of Conferences 283 (2019): 08003. http://dx.doi.org/10.1051/matecconf/201928308003.
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In this article, a hybrid method combining large eddy simulation with acoustic analogy is presented to predict three-dimensional far field noise induced by flow around a cylinder. Firstly, the governing equation including RANS equations with shear-stress transport (SST) k-ω turbulent model is numerically solved for steady flow field by using Ansys Fluent. Transient flow field is numerically solved by LES. Then, the flow field simulation results are used to compute the flow-induced noise with the FW-H integral equation method and BEM method based on Lighthill acoustic analogy equation in Actran. Before using for flow around a cylinder, accuracy of flow turbulent model in predicting turbulent flow around a cylinder is tested by comparing with available experimental data. According on the simulation result, the characteristic of the acoustic field, noise at some special points in frequency domain, the noise radiation directivity are studied. Analysis of noise distribution and frequency spectrum curves shows that dipole source takes the dominant place in the noise around a cylinder under the conditions of this article. The flow noise around a cylinder is mainly concentrated in the low frequency range.
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TALEI, MOHSEN, MICHAEL J. BREAR, and EVATT R. HAWKES. "Sound generation by laminar premixed flame annihilation." Journal of Fluid Mechanics 679 (April 18, 2011): 194–218. http://dx.doi.org/10.1017/jfm.2011.131.
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This paper presents a numerical and theoretical investigation of the sound generated by premixed flame annihilation. Planar, axisymmetric and spherically symmetric flame annihilation events are considered. The compressible Navier–Stokes, energy and progress variable equations are first solved using simple chemistry simulations, resolving both the flame dynamics and the acoustics. These simulations show that the amplitude of the far-field sound produced by the annihilation events depends on the flame thickness, particularly for the axisymmetric and spherically symmetric flame annihilation events. The flame propagation velocity is also always observed to increase significantly prior to flame annihilation, which is in keeping with other reported experimental and numerical studies. A theory is then presented that relates the far-field sound to the flame annihilation event by using a previously reported and extended form of Lighthill's acoustic analogy. A comparison with the numerical results shows that this theory accurately represents the far-field sound produced by considering only the temporal heat release source term in Lighthill's acoustic analogy, as reported by others. Additional assumptions of an infinitely thin flame and constant flame speed are then invoked in an attempt to simplify the problem. In the planar annihilation, this theory results in good predictions of the overall pressure change. However, these assumptions lead to significant under-prediction of the amplitude of far-field sound produced for the axisymmetric and spherically symmetric annihilation events. Finally, dimensional reasoning supported by the simulations and theory is used to develop scalings of the far-field sound in terms of the flame parameters.
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Lauterborn, Werner, Thomas Kurz, and Ulrich Parlitz. "Experimental Nonlinear Physics." International Journal of Bifurcation and Chaos 07, no. 09 (September 1997): 2003–33. http://dx.doi.org/10.1142/s0218127497001539.
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The review gives and account of the historical development, the current state and possible future developments of experimental nonlinear physics, with emphasis on acoustics, hydrodynamics and optics. The concepts of nonlinear time-series analysis which are the basis of the analysis of experimental outcomes from nonlinear systems are explained and recent developments pertaining to such different fields as modeling, prediction, nonlinear noise reduction, detecting determinism, synchronization, and spatio-temporal time series are surveyed. An overview is given of experiments on acoustic cavitation, a field rich of nonlinear phenomena such as nonlinear oscillations, chaotic dynamics and structure formation, and one of the first physical systems to exhibit period-doubling and chaos in experiment.
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Zhao, Yihao, Maofa Wang, Huanhuan Xue, Youping Gong, and Baochun Qiu. "Prediction Method of Underwater Acoustic Transmission Loss Based on Deep Belief Net Neural Network." Applied Sciences 11, no. 11 (May 26, 2021): 4896. http://dx.doi.org/10.3390/app11114896.
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The prediction of underwater acoustic transmission loss in the sea plays a key role in generating situational awareness in complex naval battles and assisting underwater operations. However, the traditional classical underwater acoustic transmission loss models do not consider the regional hydrological elements, and the performance of underwater acoustic transmission loss prediction under complex environmental conditions in a wide range of sea areas is limited. In order to solve this problem, we propose a deep learning-based underwater acoustic transmission loss prediction method. First, we studied the application domains of typical underwater acoustic transmission loss models (ray model, normal model, fast field program model, parabolic equation model), analyzed the constraint rules of its characteristic parameters, and constructed a dataset according to the rules. Then, according to the characteristics of the dataset, we built a DBN (deep belief net) neural network model and used DBN to train and learn the dataset. Through the DBN method, the adaptation and calculation of the underwater acoustic transmission loss model under different regional hydrological elements were carried out in a simulation environment. Finally, the new method was verified with the measured transmission loss data of acoustic sea trials in a certain sea area. The results show that the RMSE error between the underwater acoustic transmission loss calculated by the new method and the measured data was less than 6.5 dB, the accuracy was higher than that of the traditional method, and the prediction speed was faster, the result was more accurate, and had a wide range of adaptability in complex seas.
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Keiderling, Felix, Dominik Obrist, Sebastian B. Müller, and Leonhard Kleiser. "An Euler solver for the acoustic far-field prediction of compressible jet flow." PAMM 7, no. 1 (December 2007): 4120009–10. http://dx.doi.org/10.1002/pamm.200700840.
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Hu, Jing Zhu, Di Chen Liu, Qing Fen Liao, Su Wei, and Lei Yu. "Study on Acoustic Model of Transformer." Advanced Materials Research 1008-1009 (August 2014): 571–75. http://dx.doi.org/10.4028/www.scientific.net/amr.1008-1009.571.
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The model of transformer as a noise source is very critical for substation noise prediction. The transformer is equivalent to several point sources on the basis of regarding the transformer as a combination of several planar sources. This equivalent model is based on equivalent source method and it is convenient and easy. The model of 9 equivalent point sources is simulated to verify that the rebuilt sound field is roughly the same as the actual sound field generated by the plane source. Moreover, the accuracy of the model with different settings was discussed. The acoustic model is accurate and feasible to calculate the noise level radiated by transformer and it is meaningful for substation noise control.
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MCDANIEL, SUZANNE T. "COUPLED-MODE PREDICTION OF BACKSCATTER." Journal of Computational Acoustics 11, no. 04 (December 2003): 551–61. http://dx.doi.org/10.1142/s0218396x03002103.
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The application of coupled-mode theory to ocean acoustic propagation and scattering requires that ideal boundary conditions be applied at the surface and within the seabed. The depth of the lower boundary imposes limits on the ability of coupled-mode models to treat propagation and scattering at high grazing angles. Selecting this depth to predict the contributions of the continuous spectrum in a range-independent two-layered waveguide is not practical, and other methods must be introduced to apply coupled-mode theory in the near field of a source. An example of up-slope propagation in a range-dependent waveguide in which backscatter is governed by ray steepening and reversal is also treated. With a careful choice of the depth at which the lower boundary condition is applied, an estimate of the backscattered field is obtained.
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Lyu, B., A. P. Dowling, and I. Naqavi. "Prediction of installed jet noise." Journal of Fluid Mechanics 811 (December 6, 2016): 234–68. http://dx.doi.org/10.1017/jfm.2016.747.
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A semianalytical model for installed jet noise is proposed in this paper. We argue and conclude that there exist two distinct sound source mechanisms for installed jet noise, and the model is therefore composed of two parts to account for these different sound source mechanisms. Lighthill’s acoustic analogy and a fourth-order space–time correlation model for the Lighthill stress tensor are used to model the sound induced by the equivalent turbulent quadrupole sources, while the trailing-edge scattering of near-field evanescent instability waves is modelled using Amiet’s approach. A non-zero ambient mean flow is taken into account. It is found that, when the rigid surface is not so close to the jet as to affect the turbulent flow field, the trailing-edge scattering of near-field evanescent waves dominates the low-frequency amplification of installed jet noise in the far-field. The high-frequency noise enhancement on the reflected side is due to the surface reflection effect. The model agrees well with experimental results at different observer angles, apart from deviations caused by the mean-flow refraction effect at high frequencies at low observer angles.
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Afsar, Mohammed Z., Adrian Sescu, and Stewart J. Leib. "Modelling and prediction of the peak-radiated sound in subsonic axisymmetric air jets using acoustic analogy-based asymptotic analysis." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2159 (October 14, 2019): 20190073. http://dx.doi.org/10.1098/rsta.2019.0073.
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This paper uses asymptotic analysis within the generalized acoustic analogy formulation (Goldstein 2003 JFM 488 , 315–333. ( doi:10.1017/S0022112003004890 )) to develop a noise prediction model for the peak sound of axisymmetric round jets at subsonic acoustic Mach numbers (Ma). The analogy shows that the exact formula for the acoustic pressure is given by a convolution product of a propagator tensor (determined by the vector Green's function of the adjoint linearized Euler equations for a given jet mean flow) and a generalized source term representing the jet turbulence field. Using a low-frequency/small spread rate asymptotic expansion of the propagator, mean flow non-parallelism enters the lowest order Green's function solution via the streamwise component of the mean flow advection vector in a hyperbolic partial differential equation. We then address the predictive capability of the solution to this partial differential equation when used in the analogy through first-of-its-kind numerical calculations when an experimentally verified model of the turbulence source structure is used together with Reynolds-averaged Navier–Stokes solutions for the jet mean flow. Our noise predictions show a reasonable level of accuracy in the peak noise direction at Ma = 0.9, for Strouhal numbers up to about 0.6, and at Ma = 0.5 using modified source coefficients. Possible reasons for this are discussed. Moreover, the prediction range can be extended beyond unity Strouhal number by using an approximate composite asymptotic formula for the vector Green's function that reduces to the locally parallel flow limit at high frequencies. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.
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BI, Chuanxing. "Reconstruction and prediction of multi-source acoustic field with the distributed source boundary point method based nearfield acoustic holography." Science in China Series E 47, no. 2 (2004): 216. http://dx.doi.org/10.1360/02ye0127.
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Song, Xiaodong, and Qi Li. "Reconstruction of low-frequency bridge noise using an inverse modal acoustic transfer vector method." Journal of Low Frequency Noise, Vibration and Active Control 38, no. 2 (December 10, 2018): 224–43. http://dx.doi.org/10.1177/1461348418817095.
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Low-frequency noise emitted by elevated viaducts in light rail transit lines has considerable adverse effects on inhabitants living nearby. Reliable prediction of the acoustic field radiating from the viaduct using forward numerical models is challenging because the model parameters that influence viaduct vibration are difficult to obtain. To avoid directly quantifying these parameters, such as wheel–rail combined roughness, an inverse method is presented to reconstruct the acoustic field using modal acoustic transfer vectors and the sound pressures at a small number of measurement points. First, a forward numerical method based on the train–track–bridge interaction analysis is performed to predict the structure-borne noise of a concrete box girder viaduct. Then, the calculated sound pressures are treated as virtual measurement results to illustrate the inverse method procedure. Both QR decomposition and singular value decomposition with Tikhonov regularisation are used in the inverse analysis. Third, the proposed inverse method is validated by comparing the sound pressure levels computed using the inverse method with the results simulated using the forward prediction method. Finally, the reliability of the inverse procedure is further validated through field tests of two U-shaped girder viaducts.
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Gautam, Prashanta, and Abhilash J. Chandy. "A Computational Fluid Dynamics Model for Investigating Air-Pumping Mechanisms in Air-Borne Tire Noise." Tire Science and Technology 44, no. 3 (July 1, 2016): 191–211. http://dx.doi.org/10.2346/tire.16.440304.
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ABSTRACT The reduction in power train noise over the past decade has led to an increased focus in reducing tire/road noise, largely due to the environmental concerns related to road traffic noise in industrial countries. Computational fluid dynamic (CFD) simulations conducted using ANSYS FLUENT are presented here with the objective of understanding air-pumping noise-generation mechanisms due to tire/road interaction. The CFD model employs a large eddy simulation turbulence modeling approach, in which the filtered compressible Navier-Stokes equations are solved to obtain temporally and spatially accurate near-field pressure fluctuations for a two-dimensional (2D) tire geometry with (1) one groove and (2) two grooves. In addition, the Ffowcs-Williams and Hawkings (FW-H) acoustic model is used to predict far-field acoustics. The deformation of the grooves, as the tire rotates, is represented by prescribed sidewall movements. Consequently, the solution to the numerical problem is obtained through a single process, thereby enabling the prediction of small-scale air pumping, horn effect, and far-field acoustics in a single simulation. The acoustic characteristics associated with air pumping are studied through spectral analysis tools, and comparisons show that the additional groove on the horn geometry alters the spectral characteristics of air pumping. Validation of the model is conducted through qualitative and quantitative comparisons with previous studies. These simulations are intended to provide a deeper understanding about the small-scale noise generation as well as the near-field and far-field acoustics, thereby paving the way for the automotive manufacturer to compare a variety of air-related tire noise characteristics without spending time and money for vehicle pass-by tests.
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Lee, Cheong, Kim, and Kim. "Numerical Analysis and Characterization of Surface Pressure Fluctuations of High-Speed Trains Using Wavenumber–Frequency Analysis." Applied Sciences 9, no. 22 (November 15, 2019): 4924. http://dx.doi.org/10.3390/app9224924.
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The high-speed train interior noise induced by the exterior flow field is one of the critical issues for product developers to consider during design. The reliable numerical prediction of noise in a passenger cabin due to exterior flow requires the decomposition of surface pressure fluctuations into the hydrodynamic (incompressible) and the acoustic (compressible) components, as well as the accurate computation of the near aeroacoustic field, since the transmission characteristics of incompressible and compressible pressure waves through the wall panel of the cabin are quite different from each other. In this paper, a systematic numerical methodology is presented to obtain separate incompressible and compressible surface pressure fields in the wavenumber–frequency and space–time domains. First, large eddy simulation techniques were employed to predict the exterior flow field, including a highly-resolved acoustic near-field, around a high-speed train running at the speed of 300 km/h in an open field. Pressure fluctuations on the train surface were then decomposed into incompressible and compressible fluctuations using the wavenumber–frequency analysis. Finally, the separated incompressible and compressible surface pressure fields were obtained from the inverse Fourier transform of the wavenumber–frequency spectrum. The current method was illustratively applied to the high-speed train HEMU-430X running at a speed of 300 km/h in an open field. The results showed that the separate incompressible and compressible surface pressure fields in the time–space domain could be obtained together with the associated aerodynamic source mechanism. The power levels due to each pressure field were also estimated, and these can be directly used for interior noise prediction.
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SHEU, TONY W. H., and C. C. FANG. "A HIGH RESOLUTION FINITE ELEMENT ANALYSIS FOR NONLINEAR ACOUSTIC WAVE PROPAGATION." Journal of Computational Acoustics 02, no. 01 (March 1994): 29–51. http://dx.doi.org/10.1142/s0218396x9400004x.
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We investigate the application of Taylor Galerkin finite element model to simulate the propagation of impulse disturbances governed by the nonlinear Euler equations. This formulation is based on the conservation variables rather than the primitive variables so that the slowly emerging sharp acoustic profiles due to the initial fluctuation can be sharply captured. We show that when the generalized Taylor Galerkin finite element model is combined with the flux corrected transport technique of Boris and Book, the acoustic field can be more accurately predicted. The proposed prediction method was validated first by simulating different classes of transport profiles before applying it to investigate the truly nonlinear acoustic field emanating from an initial square pulse.
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MORGAN, SUSAN, DAVID J. W. HARDIE, and PATRICK C. MACEY. "A COMPARISON OF NUMERICAL METHODS FOR ACTIVE SONAR ARRAY PERFORMANCE." Journal of Computational Acoustics 09, no. 04 (December 2001): 1583–97. http://dx.doi.org/10.1142/s0218396x01001285.
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Low frequency active sonar (LFAS) arrays are complicated devices requiring careful design. Prototype LFAS arrays are expensive to construct and test. Accurate prediction of acoustic and electrical performance is therefore of great interest to LFAS designers. This generally involves solving a fully coupled problem relating the electrical drive to the resulting acoustic field. To derive results a numerical solution method is clearly the only recourse. This paper compares various numerical techniques in terms of accuracy, efficiency and overall applicability for the solution of LFAS problems. These are based around finite element (FE) and boundary element (BE) descriptions of the surrounding acoustic medium. Here we consider a pure FE approach based on wave envelope elements and a combined FE/BE scheme using an approximate BE formulation. These are contrasted with a pure BE approach that has been demonstrated to provide accurate predictions of LFAS array performance over a number of years. A piston stack transducer and a line array of free-flooding ring projectors are considered as example LFAS problems. The acoustic, structural and electrical responses are considered.
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Kamliya Jawahar, Hasan, Yujing Lin, and Mark Savill. "Large eddy simulation of airfoil self-noise using OpenFOAM." Aircraft Engineering and Aerospace Technology 90, no. 1 (January 2, 2018): 126–33. http://dx.doi.org/10.1108/aeat-05-2015-0130.
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Purpose The purpose of this paper is to investigate airfoil self-noise generation and propagation by using a hybrid method based on the large-eddy simulation (LES) approach and Curle’s acoustic analogy as implemented in OpenFOAM. Design/methodology/approach Large-eddy simulation of near-field flow over a NACA6512-63 airfoil at zero angle of attack with a boundary layer trip at Rec = 1.9 × 105 has been carried out using the OpenFOAM® computational fluid dynamics (CFD) code. Calculated flow results are compared with published experimental data. The LES includes the wind tunnel installation effects by using appropriate inflow boundary conditions obtained from a RANS κ – ω SST model computation of the whole wind tunnel domain. Far-field noise prediction was achieved by an integral method based on Curle’s acoustic analogy. The predicted sound pressure levels are validated against the experimental data at various frequency ranges. Findings The numerical results presented in this paper show that the flow features around a NACA6512-63 airfoil have been correctly captured in OpenFOAM LES calculations. The mean surface pressure distributions and the local pressure peaks for the step trip setup agree very well with the experimental measurements. Aeroacoustic prediction using Curle’s analogy shows an overall agreement with the experimental data. The sound pressure level-frequency spectral analysis produces very similar data at low to medium frequency, whereas the experimentally observed levels are slightly over predicted at a higher frequency range. Practical implications This study has achieved and evaluated an alternative aeroacoustic simulation method based on the combination of LES with a simple Smagorinsky SGS model and Curle’s analogy, as implemented in the OpenFOAM CFD code. The unsteady velocity/pressure source data produced can be used for any simpler analytically based far-field noise prediction scheme. Originality/value A complete integration of the LES and Curle’s acoustic analogy for aeroacoustic simulations has been achieved in OpenFOAM. The capability and accuracy of the hybrid method are fully evaluated for high-camber airfoil self-noise predictions. Wind tunnel installation effects have been incorporated properly into the LES.