Effects of nose shape and tunnel cross-sectional area on aerodynamic drag of train traveling in tunnels

• The aerodynamic drag of the subway train is simulated with CFD.
• When the speed of the subway train is increased, the aerodynamic drag considerably increased.
• The effects of the nose length and the tunnel cross-sectional area on the aerodynamic drag are evaluated.
• The nose length should not be longer than a certain length to reduce the drag.
• Aerodynamic drag should be considered for construction of the high-speed subway.

South Korea is proposing to construct a new public transportation system. The Great Train eXpress (GTX) will be built underground as the present subway system. However, the cruise speed will be 200 km/h. When the train speed increases in a tunnel, the aerodynamic drag significantly increases. Therefore, it is important to estimate the aerodynamic drag of the train before construction. In this study, an analysis to estimate the aerodynamic drag of the GTX is performed using Computational Fluid Dynamics (CFD). When the cruise speed increases from 100 km/h to 200 km/h, the aerodynamic drag is estimated. The effects of the train nose length and the tunnel cross-sectional area on the aerodynamic drag are also evaluated. When the train speed increases by a factor of two, the aerodynamic drag is increased approximately four times. The aerodynamic drag is reduced up to approximately 50% by changing of the nose from a blunt to a streamlined shape. The aerodynamic drag decreases up to approximately 50% again when the cross-sectional area of the tunnel increases. The tunnel cross-sectional area for construction of the proposed GTX should be larger than the current tunnel cross-sectional area. These results are applicable for the basic design of the proposed GTX and tunnel system.

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