• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.829-834
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• 2009

A ballast-flying probabilitie is suggested for various ballast types, heighter types and underbody flow conditions as train speeds. The average speed of measured points is converted to the ballast-flying probabilities of BFPF which come from wind tunnel test data. Underbody flow fields are numerically simulated for the various conditions. The results show that the ballast-flying probability is steeply increased as train speed increased, and reaches a value of 87% at 350 km/h train speed. And the differences of probabilities among the ballast shapes are considerably high. The upper surface of heighter or tie is most probable area. Through this study, the ballast-flying Sensitivities with heighter was defined to understand the characteristics of ballast-flying probability on various conditions. And the ballast-flying probability can be reduced by the heighter.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.39-44
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• 2009

The ballast-flying, induced by strong underbody flow of high-speed train, can damage train underbody, wheel and even cause the safety problems. For this reason, a heighter is being used to prevent ballast-flying through underbody flow reduction. In this research, flow field around a heighter is numerically simulated.. And the parametric study of various heighter geometries is performed to find out more effective heighter shape. Through these numerical studies, the relation between the heighter shape and underbody flow is found out. Also new heighter shapes are numerically investigated and their performances of underbody flow reduction are verified.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.109-115
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• 2012

In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.104-108
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• 2005

The Korean high speed train runs at 300 km/h, ballast-flying phenomenon often happens by strong train-wind. It is important to consider the prevention of ballast-flying phenomenon, because the train under-body and fares or walker around a rail might be damaged. In this study, Numerical analysis of the flow field of under-body of train and study of heighter-effect were conducted to decrease the speed of under-body. The shape of under-body was simplified for convenience of meshing and analysis. According to results of Taguchi's design by orthogonal arrays, a height of tie is dominant in the flow field, so if the heighter is installed on tie, the speed of under-body might be decreased. The result of this study is useful to build a new high-speed-line.

• Journal of the Korea Construction Safety Engineering Association
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• v.3 no.2 s.8
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• pp.35-45
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• 1993

• Journal of the Korean Society for Railway
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• v.8 no.1
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• pp.6-14
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• 2005

The mechanism of ballast-flying phenomena by strong wind induced by high-speed trains has extensively been investigated by conducting wind tunnel test and field-measuring of wind velocity in the vicinity of the track. The ballast gathered from the Seoul-Busan high-speed railway track has been classified by mass and shape to find relationship between those properties and the characteristic of movement in high wind and 16-channel Kiel-probe array has been used to examine the detailed flow structure above the surface of the track. The probability of ballast-flying during the passage of the high-speed train has been assessed comparing the results from wind tunnel test and that from field-measuring. The results shows that when the G7 train runs well as the KTX train runs at 300km/h, about 25m/s wind gust is induced just above the tie and the probability far small ballast under 50g to fly is about 50％ when it is on the tie. If the G7 train runs at 350km/h, the wind gust just above the tie increases to 30m/s, therefore radical countermeasure seems to be needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.369-373
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• 2005

To investigate the mechanism of ballast-flying phenomena by strong wind induced by high-speed trains, wind velocity in the vicinity of the track has been measured using 16-channel Kiel-probe array and detailed flow structure near the surface of the track has been analyzed. The position at which the underflow fully develop has been examined in order to assess the driving force of the turbulent flow under train and the results yields that the turbulent flow owing to the cavity of the inter-car as well as the friction force at the underbody of the train is the main reason of the strong wind under high-speed train. The preceding wind tunnel test results has been introduced to assess the probability of ballast-flying during the passage of the high-speed train by comparing the results from field-measuring. The results shows that when the G7 train as well as the KTX train runs at 300km/h, about 25m/s wind gust is induced just above the tie and the probability for small ballast under 50g to fly is about 50% when it is on the tie. If the G7 train runs at 350km/h, the wind gust just above the tie increases to 30m/s, therefore more radical countermeasure seems to be needed.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.229-234
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• 2004

When trains run over a snow-covered track at high speed, the snow accereted under car bodies may drop during train running. The dropped snow lumps scatter the ballast on the track damaging the car body and the environment along the track in snowy regions. In this study, various countermeasures to prevent the ballast from scattering has been investigated and compared. Furthermore, the implementation of the ballast-flying prevention methods to passing-by station has been examined through which the KTX train passes about 300km/h speed.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.874-879
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• 2004

The Korean high speed train runs at 300 km/h, ballast-flying phenomenon often happens by strong train-wind. It is important to consider the prevention of ballast-flying phenomenon, because the train under-body and fares or walker around a track might be damaged. In this study, Numerical analysis of the under-body flow field of a train and study of heighter-effect were conducted to decrease the speed of under-body. The shape of under-body was simplified for convenience of meshing and analysis. According to results of Taguchi's design by orthogonal arrays, a height of tie is dominant in the flow field, so if the heighter is installed on tie, the speed of under-body might be decreased. To apply the result of this study is useful to build a new high-speed-line might be expected.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.275-280
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• 2003

The Korean high speed train is designed to run at very high speed such as 350km/h. At this time, ballast in roadbed is dispersed by high speed air flow and this hits the substructure of the train. It becomes the factor of damaging the train. To investigate the main factor and possibility of ballast dispersion, the substructure flow is measured by Kiel-Probe Array System at G7 train experiment. And the wind tunnel experiment is performed with ballast in our research. Also CFD analysis is performed by assuming that the flow field is 2D and using simple shaped cross-tie and flat substructure of the train. By comparing the experimental results and CFD analysis, the accuracy of the analysis is checked. They will become the basic research data for the analysis and optimization of train substructure to prevent the ballast dispersion.