• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.9
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• pp.645-651
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• 2008

For a high speed train driving at 300 km/h, aero-acoustic noise is a dominant component among various noise sources. The aeroacoustic noise is mainly due to inter-coach spacings because discontinuities in the train surface significantly disturb turbulent flows. This often leads to the uncomfortableness of passengers. Interestingly, the aero-acoustic noise reduces with decreasing the mud-flap spacing of the inter-couch spacing. We perform numerical simulations to investigate flow characteristics around the inter-coach spacing. We model the inter-coach spacing as a simple 2-D cavity with flaps, and calculate the velocity and pressure field using two equation turbulence models, varying the flap spacing. The results show that a wider flap spacing develops a higher inflection point in mean velocity profiles over the cavity. It is likely that large eddies generated near the inflection point persist longer in the downstream since they are less affected by the wall. This probably induces the more aero-acoustic noises. The wider spacing also results in the larger pressure difference between the inside and outside of the cavity. This is also responsible for the increased noise since the large difference would cause a strong flow oscillations in and out of the cavity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1449-1452
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• 2006

When fluid at high speed flows over an open cavity, large acoustic pressure fields inside the cavity are produced by fluid/structure interactions at the downstream end of the cavity. The inter-coach spacing is one of the most important sources of the aero-acoustic noise of a high-speed train. This noise can usually be heard as low frequency structure-borne noise inside the train. In this study experiments were performed in order to investigate the effects of mud-flap length on the aeroacoustic noise generation inside high-speed trains. Results of the measurement confirmed that the characteristics of the noise generated from the inter-coach spacing are strongly dependent on the size of the gap. Also investigated are the characteristics of the turbulent flow after the inter-coach spacing and consequent generation of the aeroacoustic noise inside the cabin.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1259-1263
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• 2006

The inter-coach spacing is one of the most important sources of the aero-acoustic noise of a high-speed train. When fluid at high speed flows over an open cavity, such as the inter-coach spacing, large acoustic pressure fields inside the cavity are produced by fluid/structure interactions at the downstream end of the cavity. In this study experiments were performed to investigate the characteristics the aero-acoustic noise generation from the inter-coach spacing of a high-speed train. Results of the measurement confirmed that the noise generated from the gap between mud-flaps are strongly dependent on the size of the gap.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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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

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.648-649
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• 2013

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.786-791
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• 2007

Aerodynamically generated noise is dominant when the train speed approaches 300km/h. This noise sources is caused by the turbulent flow separations or vortex shedding from the train structure. Experiments were performed to investigate the characteristics of aerodynamic noise sources generated from exterior of the KTX trains and HSR-350x, especially from the inter-coach spacing. Measurements of both the inside and outside of the cabin are carried out to investigate the characteristics of the noise. Effect of the size of the mud-flap has been investigated through an wind tunnel test and it has been found that the low frequency noise is strongly dependent on the size of the gap. Also performed is an array measurement to locate different noise sources from the high-speed train. spectral characteristics of exterior noise sources are examined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.65-68
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• 2006

Experiments were performed to investigate the effects of mud-flap width on the aeroacoustic noise generation inside high-speed trains. The open-circuit type wind tunnel was used. The measurement setup was custom-built to simulate intercoach spacing. From the measurements, the characteristics of the turbulent flow after the intercoach spacing and consequent generation of aeroacoustic noise inside the cabin was investigated. Especially the effects of mud flap length on the characteristics of the characteristics of the turbulent flow were identified. The mechanism of noise generation by analyzed interactions with structure vibration characteristics and generation characteristics of blocked pressure was investigated.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.85-90
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• 2007

Aerodynamically generated noise is significant when the train speed exceeds 250km/h. Experiments were performed in order to investigate the characteristics of aerodynamic noise sources generated from exterior of the HSR-350x, especially from the inter-coach spacing. Measurements of both the inside and outside of the cabin are carried out to investigate the characteristics of the noise. Effect of the size of the gap has been investigated through an wind tunnel test and it has been found that the low frequency noise is strongly dependent on the size of gap. Also performed is an array measurement to locate different noise sources from the high-speed train. Spectral characteristics of exterior noise sources have been examined through these experiments.