• Title/Summary/Keyword: Aerodynamic Noise

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Prediction of Aerodynamic noise of Pantograph on a high-speed train using the Acoustic Analogy (음향근사기법을 이용한 고속철도 판토그래프의 공력소음 예측)

  • Han, Jae-Hyun;Kim, Tae-Min;Kim, Jeung-Tae;Kim, Jung-Soo
    • Proceedings of the KSR Conference
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    • pp.150-157
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    • 2011
  • Nowadays, high speed train has settled down as a fast and convenient environment-friendly transportation and it's need is gradually increasing. However increased train speed leads to increased aerodynamic noise, which causes critically affects comfortability of passengers. Especially, the pantograph of high speed train is protruded out of train body, which is the main factor for increased aerodynamic noise. Since aerodynamic noise caused pantograph should be measured in high speed, it is difficult to measure it and to analysis aerodynamic noise characteristics due to the various types of pantograph. In this research, aerodynamic noise of pantograph is predicted by CFD (Computational Fluid Dynamic) and FW-H (Ffowcs Williams-Hawkings) equation. Also, Wind tunnel test results and numerical simulation results were compared. As a result, Simulation results predicting sound pressure level is very similar with wind tunnel test result. This research will draw major factor in aerodynamic noise of pantograph and will be utilized for predict sound pressure level of pantograph.

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The effects of noise reduction by the change of penhead shape in pantograph (판토그래프 펜헤드 형상 변화에 따른 소음저감효과 분석)

  • Han, Jae Hyun;Kim, Tae Min;Kim, Jeung Tae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.447-453
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    • 2012
  • Nowadays, high speed train has settled down as a fast and convenient environment-friendly transportation and it's need is gradually increasing. However increased train speed leads to increased aerodynamic noise, which causes critically affects comfortability of passengers. Especially, the pantograph of high speed train is protruded out of train body, which is the main factor for increased aerodynamic noise. In this research, to reduce aerodynamic noise pantograph, panhead's shape changed to aerodynamical shape. aerodynamic noise of pantograph is predicted by CFD (Computational Fluid Dynamic) and FW-H (Ffowcs Williams-Hawkings) equation. Also, the sound pressure level of aerodynamic noise of base and modified models are predicted. And the reduction effects of the sound pressure level is analyzed.

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Prediction of the Aerodynamic Noise Generated by Pantograph on High Speed Trains (고속철도 판토그래프의 공력소음 기여도 연구)

  • Han, Jae Hyun;Kim, Tae Min;Kim, Jeung Tae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.425-431
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    • 2013
  • Nowadays, high speed train has settled down as a fast and convenient environment-friendly transportation and it's need is gradually increasing. However increased train speed leads to increased aerodynamic noise, which causes critically affects comfortability of passengers. Especially, the pantograph of high speed train is protruded out of train body, which is the main factor for increased aerodynamic noise. Since aerodynamic noise caused pantograph should be measured in high speed, it is difficult to measure it and to analysis aerodynamic noise characteristics due to the various types of pantograph. In this research, aerodynamic noise of pantograph is predicted by CFD (Computational Fluid Dynamic) and FW-H (Ffowcs Williams-Hawkings) equation. Also, Wind tunnel test results and numerical simulation results were compared. As a result, Simulation results predicting sound pressure level is very similar with wind tunnel test result. To analyze contribution of the pantograph to the noise of high-speed train, simulation results compared with measurement results of exterior noise. The simulation reuslts found that pantograph is a dominant noise source of high-speed trains's exterior noise in low frequency section. This dominant noise was come out from vortex shedding of the panhead in the pantograph. This research will be utilized for reduce sound pressure level of pantograph.

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Analysis of Aerodynamic Noise in High Speed Trains

  • Kim, Tae-Min;Kim, Jung-Soo
    • International Journal of Railway
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    • v.4 no.3
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    • pp.70-73
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    • 2011
  • 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.

An Aerodynamic Noise Reduction Design at Inter-coach Space of High Speed Trains Based on Biomimetic Analogy

  • Han, Jae-Hyun;Kim, Jung-Soo
    • International Journal of Railway
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    • v.4 no.3
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    • pp.74-79
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    • 2011
  • 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.

Measurement of aerodynamic noise of maglev vehicle models using sound camera (음향카메라를 이용한 자기부상열차 모형의 공력소음 측정)

  • Kim, Sang-Ryul;Kim, Hyun-Sil;Kim, Jae-Seung;Kang, Hyun-Ju;Kim, Bong-Ki
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.637-640
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    • 2008
  • Noise generated from maglev vehicles mainly consists of two components, one is due to mechanical noise and the other due to aerodynamic noise. The former is due to the vehicle-guideway interactions and the latter results from the unsteady air flow around the vehicle. Aerodynamic noise could become more predominant around 225 km/h for maglev vehicles. In this paper, the aerodynamic noise of maglev vehicles is investigated experimentally. The results of the wind tunnel experiments of maglev vehicle models are introduced and compared. The comparison shows that the position of the main noise is between the bottom of the vehicle model and the rail. It is also found that the emitted sound pressure level is related to the gap size between the vehicle bottom and the rail.

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Analysis of Aerodynamic Noise at Inter-coach Space of High Speed Trains

  • Kim, Tae-Min;Kim, Jung-Soo
    • International Journal of Railway
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    • v.7 no.4
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    • pp.100-108
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    • 2014
  • 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.

Analysis of aerodynamic noise at inter-coach space of high speed trains based on biomimetic analogy (생체모방공학을 적용한 고속철 차간 공간의 공력소음 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.711-716
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    • 2011
  • Today, high-speed trains enjoy wide acceptance as fast, convenient and environment-friendly means of transportation. However, increase in the speed of the train entails a concomitant increase in the aerodynamic noise, adversely affecting the passenger comfort. At the train speed exceeding 300 km/h, the effects of turbulent flows and vortex sheddding are greatly amplified, contributing to a significant increase in the aerodynamic noise. Drawing a biomimetic analogy from low-noise flight of owl, a method to reduce aerodynamic noise at inter-coach space of high-speed trains is investigated. The proposed method attempts to achieve the noise reduction by modifying the turbulent flow and vortex shedding characteristics at the inter-coach space. To determine the aerodynamic noise at various train speeds, wind tunnel testing and numerical CFD (Computational Fluid Dynamics) simulation for the basic inter-coach spacing model are carried out, and their results compared. The simulation and experimental results reveal that there are discrete frequency components associated with turbulent air flow at constant intervals in the frequency domain

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The aero-acoustic noise reduction based on biomimetics : A case study (생체모방공학을 이용한 공력 소음 저감 기초 연구)

  • Han, Jae-H.;Kim, Tae-M.;Kim, Jung-S.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.144-151
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    • 2011
  • 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 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 is 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 vorticity distribution levels which is expected to lead to varying aerodynamic noise levels.

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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

  • Han, Jae-Hyun;Kim, Tae-Min;Kim, Jung-Soo
    • International Journal of Railway
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    • v.4 no.4
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    • pp.109-115
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    • 2011
  • 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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