• Title, Summary, Keyword: Aerodynamic Noise

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Broadband Noise Analysis of Horizontal Axis Wind Turbines Including Low Frequency Noise (수평축 풍력발전기의 저주파소음을 포함한 광대역소음 해석에 관한 연구)

  • Him, Hyun-Jung;Kim, Ho-Geun;Lee, Soo-Gab
    • New & Renewable Energy
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    • v.3 no.3
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    • pp.45-53
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    • 2007
  • This paper demonstrates a computational method in predicting aerodynamic noise generated from wind turbines. Low frequency noise due to displacement of fluid and leading fluctuation, according to the blade passing motion, is modelled on monopole and dipole sources. They are predicted by Farassat 1A equation. Airfoil self noise and turbulence ingestion noise are modelled upon quadrupole sources and are predicted by semi-empirical formulas composed on the groundwork of Brooks et al. and Lowson. Aerodynamic flow in the vicinity of the blade should be obtained first, while noise source modelling need them as numerical inputs. Vortex Lattice Method(VLM) is used to compute aerodynamic conditions near blade. In the use of program X-foil [M.Drela] boundary layer characteristics are calculated to obtain airfoil self noise. Wind turbine blades are divided into spanwise unit panels, and each panel is considered as an independent source. Retarded time is considered, not only in low frequency noise but also In turbulence ingestion noise and airfoil self noise prediction. Numerical modelling is validated with measurement from NREL [AOC15/50 Turbine) and ETSU [Markham's VS45] wind turbine noise measurements.

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Internal Aerodynamic Noise from Quick Opening Throttle Valve (쓰로틀 밸브의 빠른 열림 동작에 의한 내부공력소음)

  • 정철웅;김성태;김재헌;이수갑
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.4
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    • pp.310-318
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    • 2004
  • For many industrial problems originating from aerodynamic noise, noise prediction techniques, reliable and easy to apply, would be of great value to engineers and manufacturers. General algorithm is presented for the prediction of internal flow-induced noise from quick opening throttle valve in an automotive engine. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curle's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve show good agreement with actual measurements. The results show that the dipole noise is dominant in this phenomena and the origin of noise sources is attributed to the anti-vortex lines formed in the down-stream from a throttle valve. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

Analysis of Interior Noise for KTX in Tunnel with Concrete Track (콘크리트 궤도 터널 내 KTX 차량의 실내소음 특성 분석)

  • Kim, Jae-Chul;Lee, Chan-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.25-28
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    • 2005
  • The interior noise of KTX in tunnel is becoming the problem since the commercial operating in April 2004. The major sources of interior noise for High speed train ate known as the aerodynamic noise and rolling noise generally. We measure the noise and vibration inside KTX in tunnel in order to find the cause of the interior noise of KTX. The analysis results show that the interior noise of KTX in tunnel with concrete track is increased sharply by a low frequency below 80Hz that is the natural frequency of the KTX carbody. We know that the booming noise inside KTX in tunnel with concrete track is generated by aerodynamic noise outside ganqway and rolling noise at the carbody natural frequency.

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Identifications and Reduction Methods of Aerodynamic Noise Sources in High Speed Rotating Optical Disk Drive (고속으로 회전하는 광디스크 드라이브의 공력 소음원 규명 및 소음저감방법)

  • Kim, Yong-Seok;Lee, Duck-Joo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.6
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    • pp.477-483
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    • 2007
  • Major noise source in high speed rotating optical disk drives (CD and DVD-ROM) arises due to the high-speed airflow produced from the upper and lower surfaces on the rotating disk. The present paper deals with the experimental approach how to identify the noise source based on the fundamental principles of aeroacoustics and to propose a reduction method of the noise source. The CD-ROM device is composed of disk, window tray, motors at the bottom place and electronic circuit plate also located below the window plate. The window is cut in the tray to read the disk information using the optical device located below the tray and moving linearly from the center of the disk through the end of the disk. All components are possible noise generators. Experimental studies were carried out in the anechoic room with various design modifications, such as tray geometry, window size and hole location on tray, to identify the major aerodynamic noise source and significant reductions of the aerodynamic noise were obtained.

Aerodynamic Noise Prediction of Automobile Engine Cooling Fan Noise (자동차 엔진 냉각홴의 공력 소음 예측에 관한 연구)

  • Lee, Jeonghan;Cho, Kyungseok;Sun, Hyosung;Shin, Hyungki;Lee, Soogab
    • 유체기계공업학회:학술대회논문집
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    • pp.115-120
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    • 1998
  • Aerodynamic noise generated by automobile cooling fan is investigated. Automobile cooling fans radiate both discrete frequency noise as well as broadband noise. In the present work, the former is considered through free-wake panel method coupled with acoustic analogy fully considering the retarded time variation on the blade surface, while the latter is taken into account by three well-established broadband noise components. Experiments were performed to supplement necessary inputs as well as to provide the final comparison with the predicted noise spectrum. The predicted noise levels at blade passing frequencies agree well with the experimental data for the first few harmonics. Although the predicted broadband noise levels at higher frequencies fall below the experimental data due to the fundamental shortcomings of the utilized formulations, the analysis offers a detailed physical understanding of the fan noise generation processes.

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Aerodynamic Noise Analysis of High Speed Wind Turbine System for Design Parameters of the Rotor Blade (고속 회전 풍력 시스템의 로터 설계 인자에 따른 공력 소음 해석 연구)

  • Lee, Seung-Min;Kim, Ho-Geon;Son, Eun-Kuk;Lee, Soo-Gab
    • 한국신재생에너지학회:학술대회논문집
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    • pp.521-524
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    • 2009
  • This study describes aerodynamic noise of high speed wind turbine system, which is invented as a new concept in order to reduce the torque of main shaft, for design parameters of the rotor blade. For parametric study of high speed rotor aerodynamic noise, Unsteady Vortex Lattice Method with Nonlinear Vortex Correction Method is used for analysis of wind turbine blade aerodynamic and Farassat1A and Semi-Empirical are used for low frequency noise and airfoil self noise. Parameters are chord length, twist and rotational speed for this parametric research. In the low frequency range, the change of noise is predicted the same level as each parameters varies. However, in case of broadband noise of blade, the change of rotational speed makes more variation of noise than other parameters. When the geometric angles of attack are fixed, as the rotational speed is increased by 5RPM, the noise level is increased by 4dB.

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Hyundai Motor's 4th NVH open BMT - Wind noise prediction on the HSM (Hyundai simplified model) using Ansys Fluent and LMS Virtual.Lab

  • Hallez, Raphael;Lee, Sang Yeop;Khondge, Ashok;Lee, Jeongwon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.562-562
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    • 2014
  • Assessment of aerodynamic noise is becoming increasingly important for automotive manufacturers. Flow passing a vehicle may indeed lead to high interior noise level and affect cabin comfort. Interior noise results from various mechanisms including aerodynamic fluctuations of the disturbed flow around the side mirror or pillar, hydrodynamic and acoustic loading of the car panels and windows, vibration of these panels and acoustic radiation inside the vehicle. Objective of the present study is to capture these important mechanisms in a simulation model and demonstrate the ability of the combined simulation tools Fluent / Virtual.Lab to provide accurate aerodynamic and interior noise prediction results. Previous study focused on the noise generated by the turbulence around the A-pillar structure of the HSM (Hyundai simplified model). The present study also includes the effect of the side-mirror and rain-gutter structures. Complete modeling process is presented including details on the unsteady CFD simulation and the vibro-acoustic model with absorption materials. Guidelines and best practices for building the simulation model are also discussed.

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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 (생체모방공학을 이용한 고속철도 차간 공간에 적용한 부엉이 깃 형상 크기에 따른 공력소음 저감 연구)

  • HAn, Jae-Hyun;Kim, Tae-Min;Kim, Jung-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.606-611
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    • 2012
  • An analysis and design method for reducing aerodynamic noise in high-speed trains based on biomimetics of noiseless flight of owl is proposed. Wind tunnel testing and numerical CFD (Computational Fluid Dynamics) simulation for the basic inter-coach spacing model are carried out, and their results compared. To determine the effect of scaling of the owl's flight feather on the noise reduction, 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 dB, while two-fold increase in length dimensions reduces the noise by 12 dB. Validation of numerical solution using wind tunnel experimental measurements are presented as well.

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Numerical Prediction of Aerodynamic Noise from Rotors (회전익 공력소음의 수치적 예측)

  • 이정한;이수갑
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.581-587
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    • 1997
  • Numerical predictions of aerodynamic noise radiated by subsonic rotors are carried out. A time domain approach for Ffowcs-Williams Hawkings equation of acoustic analogy is used in developing a comprehensive rotor/fan noise prediction program to handle both arbitrary blade shapes and loading conditions. Since only the aeroacoustic aspects of rotors are considered here, the calculations are carried out for rotors with simple aerodynamic characteristics. Broadband noise from ingestion of turbulence is also considered. By incorporating discrete frequency noise prediction of steady loading with broadband spectrum, much better correlation at the low frequency region with experimental data is obtaind. The contributions from different noise mechanisms can also be analysed through this method.

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Aerodynamic Noise Characteristics of High-speed Trains by the Beamforming Method (빔형성 기법을 이용한 고속철도차량의 공력소음특성 도출 연구)

  • Noh, Hee-Min;Choi, Sung-Hoon;Koh, Hyo-In;Hong, Suk-Yoon
    • Journal of the Korean Society for Railway
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    • v.15 no.3
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    • pp.231-236
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    • 2012
  • In this paper, aerodynamic noise characteristics of high-speed trains were deduced from the beamforming method. First, pass-by noise of high-speed trains was measured by a microphone array system. This measurement suggested that the majority of the aerodynamic noise produced came from the bogie area, the pantograph and its cover, and inter-coach gaps. Then, beampower outputs of a position in high-speed trains were obtained from the beamforming method. By Fourier transform, sound characteristics of the position in the frequency domain were deduced from the beamforming power spectrum. From this study, aerodynamic noise characteristics from the major sources of high-speed trains were drawn.