Comparative study on the effect of aerodynamic braking plates mounted at the inter-carriage region of a high-speed train with pantograph and air-conditioning unit for enhanced braking

In this study, we analyse the unsteady flow around a 1/8th-scaled uniform vehicle model with three configurations of aerodynamic braking plates mounted at the inter-carriage region. In addition, the study aims at determining an appropriate plate configuration to obtain an increasing effect of aerodynamic drag and analyses the effect of plates on the flow field at the top of the vehicle, where a pantograph and an air-conditioning unit are installed. Improved delayed detached eddy simulations are conducted with shear-stress transport K-omega turbulence model, and the results are compared with the experimental data and grid independence to validate the reliability of the obtained solution. Furthermore, the aerodynamic drag of the vehicles is significantly increased when the plates are opened and the aerodynamic braking distance is significantly decreased, especially for the single large plate mounted downstream of the inter-carriage region, followed by the single large plate mounted at the upstream of the inter-carriage region. In addition, the flow field around the inter-carriage region is more sensitive to the size of plates than their location. Both the pantograph and air-conditioning unit restrict the development of airflow downstream of the plates, and should thus be located as far away from the inter-carriage region as possible. Although the pantograph-catenary system would be affected by the opening of plates, the effect is not very large. The findings of this study can also be conducive to help engineers design and operate an optimal aerodynamic braking system.