• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.2
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• pp.188-200
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• 2018

This paper proposes a single control strategy to solve the problem of trans-media vehicle difficult control. The proposed control strategy is just to control the vehicle's air navigation, but not to control the underwater navigation. The hydrodynamic model of a vehicle when entering water obliquely at low speed has been founded to analyze the motion characteristics. Two methods have been used to simulate the vehicle entering water in the same condition: numerical simulation method and theoretical model solving method. And the results of the two methods can validate the hydrodynamic model founded in this paper. The entering water motion in the conditions of different velocity, different angle, and different attack angle has been simulated by this hydrodynamic model and the simulation has been analyzed. And the change rule of the vehicle's gestures and position when entering water has been obtained by analysis. This entering water rule will guide the follow-up of a series of research, such as the underwater navigation, the exiting water process and so on.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.1039-1046
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• 2006

The numerical simulations on the train entering a tunnel are performed by solving unsteady axi-symmetric problems. To reduce the effects of the pressure wave generated by the train starting abruptly, several starting methods of the train are examined. The high order velocity increase gives better results than those for the linear velocity increase. The high order velocity increase gives good results for the pressure rise by the train entering a tunnel, too. The distance to the train reaches the highest running velocity from the start should be more than 60 m when the train speed is 350 km/h.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.333-343
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• 1999

When a high speed train enters a tunnel, wind speed passing through the train in a tunnel section becomes higher due to the reverse flow to the direction of the train. The higher wind speed gives more aerodynamic forces to the pantograph on the train. Therefore, it is necessary to perform aerodynamic and dynamic analyses in order to check whether the current collection of the high speed train, entering the tunnel, still remain permissible or not. In this paper, the aerodynamic analysis has been performed under the assumption that a high speed train at 300 km/h enters a tunnel whose cross sectional area Is 107/㎡ and length is 1000m. In consideration of the aerodynamic analysis results, the dynamic analysis has been performed based on the catenary and pantograph dynamic models in SEOUL-PUSAN high speed rail, using the GASENDO developed by RTRI. In addition, the fatigue life of the contact wire has been reviewed using the Goodman diagram. Based on the analysis results, it is concluded that the increase of the aerodynamic forces on the pantograph in the tunnel section shall not affect characteristics of current collection adversely except that motions of the pantograph may be constrained by bump-stops.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.189-192
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• 2006

The numerical simulations on the train entrering a tunnel were performed by solving unsteady axi-symmetric problems. To reduce the effects of the pressure wave generated by the train starting abruptly, several starting method of the train were also examined. The pressure rise by the train entering a tunnel was compared with other results, and similar value was obtained compared with those of previous studies.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.91-98
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• 2000

The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the flow field and compression wave around the high speed train which Is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation around the nose region was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed and presented.

• Journal of computational fluids engineering
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• v.5 no.3
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• pp.23-31
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• 2000

The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the viscous flow field and compression wave around the high speed train which is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation owing to the viscous interaction around the train was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed.

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.17-21
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• 2006

The numerical simulations on the train entering a tunnel were performed by solving unsteady axi-symmetric problems. In the case that 5th order velocity profile is used to reduce the effects of the pressure wave generated by the train starting abruptly, the effect of the initial distance between the train and the tunnel were examined. The impulsive start gives undesired pressure disturbances to the flow field including inside the tunnel. But 5th order velocity profile with initial distance more than 80 m gives much stable pressure variance in time, and pressure distribution inside the tunnel in space. The distance to the train reaches the highest running velocity from the start should be more than 80 m when the train speed is 350 km/h.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3672-3679
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• 2015

The heat generated by electrical components during train operation was estimated by measuring the wall temperature in a locomotive, as well as the temperature and speed of the air entering from the outside and then returning to the outside. The temperatures of the electrical components and wall surface in a high-speed train were measured using an infrared camera. The heat generated by the electrical components was exhausted to the outside through a duct installed on the ceiling of the high-speed train. Thus, the temperature and speed of this exhaust air were measured, as well as those of the air entering the locomotive from the outside. The temperatures at the surfaces of the electrical components and walls in the locomotive were also measured using an attachment-type temperature sensor. In addition, the measurement results were applied to analyze how the heat characteristics of the electrical components were affected by the train operation.

• Journal of Korean Society of Transportation
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• v.33 no.1
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• pp.14-28
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• 2015

Numerous research has been conducted using internet search data since the mid-2000s. For example, Google Inc. developed a service predicting influenza patterns using the internet search data. The main objective of this study is to prove the hypothesis that highway traffic indices are similar to the internet search patterns. In order to achieve this objective, a model to predict the number of vehicles entering the expressway and space-mean speed was developed and the goodness-of-fit of the model was assessed. The results revealed several findings. First, it was shown that the Google search traffic was a good predictor for the TCS entering traffic volume model at sites with frequent commute trips, and it had a negative correlation with the TCS entering traffic volume. Second, the Naver search traffic was utilized for the TCS entering traffic volume model at sites with numerous recreational trips, and it was positively correlated with the TCS entering traffic volume. Third, it was uncovered that the VDS speed had a negative relationship with the search traffic on the time series diagram. Lastly, it was concluded that the transfer function noise time series model showed the better goodness-of-fit compared to the other time series model. It is expected that "Big Data" from the internet search data can be extensively applied in the transportation field if the sources of search traffic, time difference and aggregation units are explored in the follow-up studies.

• Journal of KSNVE
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• v.7 no.6
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• pp.959-966
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• 1997

In general, the booming noise intensity at tunnel exit is strongly related to the gradient of the compression wave front created by high speed train entering the tunnel. This paper presents some results in relation with the compression wave front produced when the high speed train enters a tunnel. Four kinds of tunnel entrance shape with real dimensions were studied to investigate the formation of compression wave front inside tunnel by train entering tunnel. Computations were carried out using three-dimensional compressible Euler equation with vanishing viscosity and conductivity of fluid. According to the results, the flow disturbances occured at tunnel entrance were eliminated by tunnel hood with same cross sectional area. The compression wave front is formed completely at 30-40m from tunnel entrance. The maximum pressure gradient of compression wave front is reduced by 29.8% for the inclined tunnel hood and reduced by 21.5% for the tunnel hood with holes at the top face with tunnel without hood. The length of the inclined hood is 15m and the length of the hood with holes is 20m.