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Soogab Lee - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study of Aerodynamic Noise by a small wind turbine
Renewable Energy, 2014Co-Authors: Seunghoon Lee, Soogab LeeAbstract:To examine the Aerodynamic Noise produced by small wind turbines, this study predicts and measures the Aerodynamic Noise from a 10 kW wind turbine. The numerical predictions include the turbulence ingestion Noise, turbulent-boundary-layer trailing edge Noise, and trailing edge bluntness Noise. The Noise measurement is carried out with free-field microphones at a reference position according to the IEC 61400-11 standard. Although the trailing edge bluntness Noise is under-predicted at low wind speeds, the spectral trends of the prediction results generally agree well with those of the experimental data. It is also found that for small wind turbines, the trailing edge bluntness Noise can be an important Noise source.
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numerical modeling of wind turbine Aerodynamic Noise in the time domain
Journal of the Acoustical Society of America, 2013Co-Authors: Seunghoon Lee, Seungmin Lee, Soogab LeeAbstract:Aerodynamic Noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge Noise model is used to determine the unsteady pressure on the blade surface. The far-field Noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional Noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine Noise can be quite different with respect to the distance and direction from the wind turbine.
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Aerodynamic Noise analysis of large horizontal axis wind turbines considering fluid structure interaction
Renewable Energy, 2012Co-Authors: Hogeon Kim, Seungmin Lee, Seunghoon Lee, Eunkuk Son, Soogab LeeAbstract:Aerodynamic Noise is one of the most serious barriers in wind energy development. To develop technologies for wind turbine Noise reduction and assessment, Noise needs to be predicted precisely with special consideration given to blade flexibility. The numerical tool, WINFAS, which can simulate fluid–structure interaction, consists of three parts: the first part, the Unsteady Vortex Lattice Method, analyzes Aerodynamics; the second part, the Nonlinear Composite Beam Theory, analyzes structure; and the third part uses a semi-empirical formula to analyze airfoil self-Noise and the Lowson’s formula to analyze turbulence ingestion Noise. In this study, using this numerical tool, the change in the Noise strength due to blade flexibility was examined. This research showed that elastic blades decreased broadband Noise because pitching motion reduced the angle of attack.
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analysis and optimization of Aerodynamic Noise in a centrifugal compressor
Journal of Sound and Vibration, 2006Co-Authors: Hyosung Sun, Hyungki Shin, Soogab LeeAbstract:Abstract The numerical methods for the performance analysis and the Noise prediction of the centrifugal compressor impeller are developed, which are coupled with the optimization design methodology consisting of response surface method, statistical approach, and genetic algorithm. Navier–Stokes equations with the two-equation ( k – ω ) turbulence model are applied to calculate impeller Aerodynamic characteristics, and Ffowcs Williams–Hawkings formulation and boundary element method are used to predict the impeller Aerodynamic Noise on the basis of impeller flow field results. The computational codes are verified through the comparison of measured data. The quadratic response surface model with D-optimal three-level factorial experimental design points is constructed to optimize the impeller geometry for the advanced centrifugal compressor, and it is shown that the quadratic model exhibits a reasonable fitting quality resulting in the impeller blade design with the high performance and the low far-field Noise level. The influences of selected design variables and their mutual interactions as well as the effects of various objective functions and constraints on the impeller performance and the impeller Noise are also examined as a result of the optimization process.
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Computation of internal Aerodynamic Noise from a quick-opening throttle valve using frequency-domain acoustic analogy
Applied Acoustics, 2005Co-Authors: Jewook Ryu, Cheolung Cheong, Sungtae Kim, Soogab LeeAbstract:Recently, plastic products in air-intake parts of automotive engines have become very popular due to advantages that include reduced weight, constricted cost, and lower intake air temperature. However, flow-induced Noise in air-intake parts becomes a more serious problem for plastic intake-manifolds than for conventional aluminum-made manifolds. This is due to the fact that plastic manifolds transmit more Noise owing to their lower material density. Internal Aerodynamic Noise from a quick-opening throttle valve is computed by using a frequencydomain acoustic analogy, which is based on the integral formula derived by using the General Green Function, Lighthills acoustic analogy and Curles extension of Lighthills. The integral formula is arranged in such a manner that allows a frequency-domain acoustic signal to be predicted at any location in a duct through the use of unsteady flow data in space and time,
Seunghoon Lee - One of the best experts on this subject based on the ideXlab platform.
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numerical and experimental study of Aerodynamic Noise by a small wind turbine
Renewable Energy, 2014Co-Authors: Seunghoon Lee, Soogab LeeAbstract:To examine the Aerodynamic Noise produced by small wind turbines, this study predicts and measures the Aerodynamic Noise from a 10 kW wind turbine. The numerical predictions include the turbulence ingestion Noise, turbulent-boundary-layer trailing edge Noise, and trailing edge bluntness Noise. The Noise measurement is carried out with free-field microphones at a reference position according to the IEC 61400-11 standard. Although the trailing edge bluntness Noise is under-predicted at low wind speeds, the spectral trends of the prediction results generally agree well with those of the experimental data. It is also found that for small wind turbines, the trailing edge bluntness Noise can be an important Noise source.
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numerical modeling of wind turbine Aerodynamic Noise in the time domain
Journal of the Acoustical Society of America, 2013Co-Authors: Seunghoon Lee, Seungmin Lee, Soogab LeeAbstract:Aerodynamic Noise from a wind turbine is numerically modeled in the time domain. An analytic trailing edge Noise model is used to determine the unsteady pressure on the blade surface. The far-field Noise due to the unsteady pressure is calculated using the acoustic analogy theory. By using a strip theory approach, the two-dimensional Noise model is applied to rotating wind turbine blades. The numerical results indicate that, although the operating and atmospheric conditions are identical, the acoustical characteristics of wind turbine Noise can be quite different with respect to the distance and direction from the wind turbine.
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Aerodynamic Noise analysis of large horizontal axis wind turbines considering fluid structure interaction
Renewable Energy, 2012Co-Authors: Hogeon Kim, Seungmin Lee, Seunghoon Lee, Eunkuk Son, Soogab LeeAbstract:Aerodynamic Noise is one of the most serious barriers in wind energy development. To develop technologies for wind turbine Noise reduction and assessment, Noise needs to be predicted precisely with special consideration given to blade flexibility. The numerical tool, WINFAS, which can simulate fluid–structure interaction, consists of three parts: the first part, the Unsteady Vortex Lattice Method, analyzes Aerodynamics; the second part, the Nonlinear Composite Beam Theory, analyzes structure; and the third part uses a semi-empirical formula to analyze airfoil self-Noise and the Lowson’s formula to analyze turbulence ingestion Noise. In this study, using this numerical tool, the change in the Noise strength due to blade flexibility was examined. This research showed that elastic blades decreased broadband Noise because pitching motion reduced the angle of attack.
D J Thompson - One of the best experts on this subject based on the ideXlab platform.
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reduction of Aerodynamic Noise from square bars by introducing spanwise waviness
Journal of Sound and Vibration, 2018Co-Authors: Xiaowan Liu, D J Thompson, Vincent JurdicAbstract:Abstract This paper presents an investigation, using both numerical and experimental methods, of the application of spanwise waviness to reduce Aerodynamic Noise from square bars. The numerical simulations are performed using the Delayed Detached-Eddy Simulation approach to obtain the near-field unsteady flow properties, which are then used to calculate the equivalent source terms in the Ffowcs Williams-Hawkings equation for far-field Noise prediction. For a straight square bar in cross-flow, which produces strong tonal Noise associated with the vortex shedding, a benchmark study shows good agreement between numerical simulations and measurements in terms of far-field Noise spectra. Waviness is then introduced along the bar span and the influence of the amplitude and wavelength of the waviness is studied. When the wave amplitude is nearly half the bar width, a large Noise reduction of as much as 30 dB is found from both numerical simulations and measurements, including a 10 dB reduction in the broadband level. The influence of the wavelength is much smaller. Analysis of the flow features show that, with increased wave amplitudes, the spanwise flow becomes significant and strong crossflow vortices develop in the near wake which effectively suppress the primary vortex shedding. This reduces the Noise level significantly, especially the tonal Noise associated with the vortex shedding.
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component based model to predict Aerodynamic Noise from high speed train pantographs
Journal of Sound and Vibration, 2017Co-Authors: Latorre E Iglesias, D J Thompson, Malcolm SmithAbstract:At typical speeds of modern high-speed trains the Aerodynamic Noise produced by the airflow over the pantograph is a significant source of Noise. Although numerical models can be used to predict this they are still very computationally intensive. A semi-empirical component-based prediction model is proposed to predict the Aerodynamic Noise from train pantographs. The pantograph is approximated as an assembly of cylinders and bars with particular cross-sections. An empirical database is used to obtain the coefficients of the model to account for various factors: incident flow speed, diameter, cross-sectional shape, yaw angle, rounded edges, length-to-width ratio, incoming turbulence and directivity. The overall Noise from the pantograph is obtained as the incoherent sum of the predicted Noise from the different pantograph struts. The model is validated using available wind tunnel Noise measurements of two full-size pantographs. The results show the potential of the semi-empirical model to be used as a rapid tool to predict Aerodynamic Noise from train pantographs.
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anechoic wind tunnel tests on high speed train bogie Aerodynamic Noise
International Journal of Rail Transportation, 2017Co-Authors: Eduardo Latorre Iglesias, D J Thompson, Malcolm Smith, Toshiki Kitagawa, Nobuhiro YamazakiAbstract:ABSTRACTAerodynamic Noise becomes a significant Noise source at speeds normally reached by high-speed trains. The train bogies are identified as important sources of Aerodynamic Noise. Due to the difficulty to assess this Noise source carrying out field tests, wind tunnel tests offer many advantages. Tests were performed in the large-scale low-Noise anechoic wind tunnel at Maibara, Japan, using a 1/7 scale train car and bogie model for a range of flow speeds between 50, 76, 89 and 100 m/s. The dependence of the Aerodynamic Noise from the bogie region on different factors has been studied for different bogie configurations and inflow conditions representing different positions of the bogie along the train. The speed dependence and the Noise directivity have also been assessed. The results show the particular importance of the components exposed to the free flow, whereas those shielded within the bogie cavity are shown to radiate much less Noise.
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the effect of a moving ground on the flow and Aerodynamic Noise behaviour of a simplified high speed train bogie
International Journal of Rail Transportation, 2017Co-Authors: Jianyue Zhu, D J ThompsonAbstract:ABSTRACTAeroacoustic sources around the train bogie area are particularly important but involve complex flow. In this study, a numerical investigation is presented of the effect of a moving ground on the flow and aeroacoustic Noise behaviour of a train bogie. These make use of the delayed detached-eddy simulation (DDES) combined with an acoustic analogy for Noise prediction. First, the flow around an isolated wheel set (1:5 scale) is calculated when it is in proximity to the ground and this is compared with wind-tunnel measurements to verify the simulation. Then the flow and Aerodynamic Noise behaviour of a simplified high-speed train bogie at scale 1:10 with and without the ground underneath are studied numerically. It is found that a highly turbulent flow is generated within the bogie cavity and the ground increases the Noise levels by 6–8 dB due to a combination of acoustic reflection from the ground and modifications to the flow.
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experimental study of the Aerodynamic Noise radiated by cylinders with different cross sections and yaw angles
Journal of Sound and Vibration, 2016Co-Authors: Latorre E Iglesias, D J Thompson, Malcolm SmithAbstract:Vortex shedding from cylinders has been extensively studied due to its occurrence in many engineering fields. Many experimental studies reported in the literature focus on the Aerodynamics of the vortex shedding process but the literature about the radiated Noise is more scarce. The aim of the work presented here is to extend the available Noise data. Aero-acoustic wind tunnel tests were carried out using cylinders with different cross-sections: circular, square, rectangular and elliptical. Flow speeds between 20 and 50 m/s were used, corresponding to Reynolds numbers in the range from 1.6×104 to 1.2×105. The dependence of the Noise on the yaw angle, flow speed, cross-sectional shape, angle of attack and radiation angle (directivity) is assessed. The results obtained are compared, where possible, with those found in the literature for similar cases. It is intended that the results can be used for the validation and calibration of numerical and empirical Aerodynamic Noise prediction models.
Jungsoo Kim - One of the best experts on this subject based on the ideXlab platform.
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analysis of Aerodynamic Noise at inter coach space of high speed trains
International Journal of Railway, 2014Co-Authors: Taemin Kim, Jungsoo KimAbstract:A numerical analysis method for predicting Aerodynamic Noise at inter-coach space of high-speed trains, validated by wind-tunnel experiments for limited speed range, is proposed. The wind-tunnel testing measurements of the train Aerodynamic sound pressure level for the new generation Korean high-speed train have suggested that the inter-coach space Aerodynamic Noise varies approximately to the 7.7th power of the train speed. The observed high sensitivity serves as a motivation for the present investigation on elucidating the characteristics of Noise emission at inter-coach space. As train speed increases, the effect of turbulent flows and vortex shedding is amplified, with concomitant increase in the Aerodynamic Noise. The turbulent flow field analysis demonstrates that vortex formation indeed causes generation of Aerodynamic sound. For validation, numerical simulation and wind tunnel measurements are performed under identical conditions. The results show close correlation between the numerically derived and measured values, and with some adjustment, the results are found to be in good agreement. Thus validated, the numerical analysis procedure is applied to predict the Aerodynamic Noise level at inter-coach space. As the train gains speed, numerical simulation predicts increase in the overall Aerodynamic sound emission level accompanied by an upward shift in the main frequency components of the sound. A contour mapping of the Aerodynamic sound for the region enclosing the inter-coach space is presented.
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the effect of scaling of owl s flight feather on Aerodynamic Noise at inter coach space of high speed trains based on biomimetic analogy
International Journal of Railway, 2011Co-Authors: Jaehyun Han, Taemin Kim, Jungsoo KimAbstract:An analysis and design method for reducing Aerodynamic Noise in high-speed trains based on biomimetics of Noiseless flight of owl is proposed. Five factors related to the morphology of the flight feather have been selected, and the candidate optimal shape of the flight feather is determined. The turbulent flow field analysis demonstrates that the optimal shape leads to diminished vortex formation by causing separation of the flow as well as allowing the fluid to climb up along the surface of the flight feather. To determine the effect of scaling of the owl’s flight feather on the Noise reduction, a two-fold and a four-fold scaled up model of the feather are constructed, and the numerical simulations are carried out to obtain the Aerodynamic Noise levels for each scale. Original model is found to reduce the Noise level by 10 dBA, while two-fold increase in length dimensions reduces the Noise by 12 dBA. Validation of numerical solution using wind tunnel experimental measurements is presented as well.
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analysis of Aerodynamic Noise in high speed trains
International Journal of Railway, 2011Co-Authors: Taemin Kim, Jungsoo KimAbstract:Controlling the exterior and interior Noise emission has become an important issue in the research and development of high speed trains. As the operating speed of the train increases, the Noise emission characteristics are expected to deviate from that of the existing trains due to several changes in the basic train layout. For train speed in excess of 350 km/h in particular, the Aerodynamic Noise component starts to exceed the structure-borne Noise component, and even an incremental speed increase is accompanied by a rapid elevation in the Noise level. The present study presents an engineering approach for predicting the Aerodynamic Noise level at the design stage for high speed trains. The experimental Noise measurements from test run of Korean high speed train under development are presented as a partial validation of the proposed approach. While the overall Aerodynamic Noise can be cast in a single power law relationship against the train speed, different parts of the train show power law relationships unique to each component.
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an Aerodynamic Noise reduction design at inter coach space of high speed trains based on biomimetic analogy
International Journal of Railway, 2011Co-Authors: Jaehyun Han, Jungsoo KimAbstract:Recent years have witnessed speed up of moving vehicles such as high-speed of trains. Increase in speed entails concomitant increase in turbulent air flow which contributes toward increased Aerodynamic Noise. The proposed method for Aerodynamic Noise reduction is based on a biomimetic design of owl feather. The five morphological parameters of the owl feather are extracted from close observation, and simulation cases are constructed by applying design of experiments methodology. Swirling strength for each case is obtained through steady-state CFD analysis, and key morphological parameters that affect the turbulence are identified. Large eddy simulations (LES) are then performed on selected cases to predict the air turbulence. Different cases show varying vortex distributions which are expected to lead to varying Aerodynamic Noise levels.
Hyungki Shin - One of the best experts on this subject based on the ideXlab platform.
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Numerical simulation of flatback airfoil Aerodynamic Noise
Renewable Energy, 2014Co-Authors: Minu Jeon, Hyungki ShinAbstract:The present paper presents a possible path for developing a large eddy simulation (LES) applicable to high Reynolds-number complex turbulent flows and the performance of the coupling of LES with statistical turbulence models around the flow over a blunt trailing edge configuration. The turbulent fluctuations in the boundary layers at the inflow region of the LES domain are generated by a synthesized turbulence method. The hybrid RANS-LES model showed considerable improvement in prediction accuracy even at a moderate grid resolution. The Aerodynamic comparison with experimental data shows like results for the pressure distributions surrounding a flatback airfoil. To predict accurately the Noise radiation from the blunt trailing edge and to save computational costs, the near-field region is computed by embedded LES while the surrounding region is simultaneously computed by RANS. The Brooks, Pope, and Marcolini (BPM) semi-empirical model is used for Noise comparison with the hybrid RANS-LES result and experimental data. The present hybrid RANS-LES method is found to be adequate for predicting Aerodynamic Noise generation by vortical flow in the vicinity of a blunt trailing edge airfoil over a range of frequencies.
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analysis and optimization of Aerodynamic Noise in a centrifugal compressor
Journal of Sound and Vibration, 2006Co-Authors: Hyosung Sun, Hyungki Shin, Soogab LeeAbstract:Abstract The numerical methods for the performance analysis and the Noise prediction of the centrifugal compressor impeller are developed, which are coupled with the optimization design methodology consisting of response surface method, statistical approach, and genetic algorithm. Navier–Stokes equations with the two-equation ( k – ω ) turbulence model are applied to calculate impeller Aerodynamic characteristics, and Ffowcs Williams–Hawkings formulation and boundary element method are used to predict the impeller Aerodynamic Noise on the basis of impeller flow field results. The computational codes are verified through the comparison of measured data. The quadratic response surface model with D-optimal three-level factorial experimental design points is constructed to optimize the impeller geometry for the advanced centrifugal compressor, and it is shown that the quadratic model exhibits a reasonable fitting quality resulting in the impeller blade design with the high performance and the low far-field Noise level. The influences of selected design variables and their mutual interactions as well as the effects of various objective functions and constraints on the impeller performance and the impeller Noise are also examined as a result of the optimization process.