Effects of bottom deflectors on aerodynamic drag reduction of a high-speed train

Inspired by the fact that bogies and bottom equipment generally contribute a great deal of aerodynamic drag to high-speed trains, this paper puts forward a simple method of mounting some small deflectors before and/or after the bogie cabins to optimize the underbody flow and reduce the aerodynamic drag of high-speed trains. The flow fields of the high-speed train models with and without bottom deflectors are numerically studied by the IDDES method. The effectiveness and further mechanism of the bottom deflectors on aerodynamic drag reduction are analyzed. It is demonstrated that the bottom deflectors could guide the underbody flow to the ground and prevent it from hitting on the bogies and bottom equipment of the train, resulting in a significant aerodynamic drag reduction effect. Moreover, the effects of different mounting locations of bottom deflectors on drag reduction are discussed as well, and an optimal mounting configuration with a drag reduction effect of up to about 12% is finally obtained. Nevertheless, the mounted deflector is also proved capable of significantly reducing the interference range of the underbody flow and reducing the slipstream of the train, which possesses a higher guarantee for the safety of railway workers and passengers waiting on the platforms. This work provides a new idea for aerodynamic drag reduction of high-speed trains, and is of great significance in energy conservation and consumption reduction.