• 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.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.