A novel bionic Coleoptera pantograph deflector for aerodynamic drag reduction of a high-speed train

As an important source of train aerodynamic drag, the pantograph area is a key region which takes up about 10% contribution of the total. Thus, improving the pressure distribution in the pantograph area becomes a potential and effective method of reducing train aerodynamic drag. Based on the biological pattern of Coleoptera, a novel bionic elytron (i. e., deflector) installed on the pantograph areas of an eight-car grouping high-speed train was proposed to smooth the flow. Four calculation cases were set up, i. e., the original model (Model I), pantograph I with a deflector (Model II), pantograph II with a deflector (Model III), and pantograph I and II with deflectors (Model IV), to explore the mechanism of aerodynamic drag reduction for the train and improve its aerodynamic performance. The results show that after installing the pantograph deflector the aerodynamic drag force of the pantograph area is significantly reduced. The maximum drag reduction in pantograph I region is up to 84.5%, and the maximum drag reduction in pantograph II region is 25.0%. When the deflectors are installed in both pantograph I and pantograph II areas, the total drag reduction in pantographs I and II areas can be achieved by 49.6%. The air flows over the pantograph area in a smoother way with less blockage effect as compared to the base case without deflectors. However, the downstream flow velocity speeds up and impacts the corresponding region, e.g., windshields, leading to an increase of aerodynamic drag. When the deflector is installed in the area of pantograph I or pantograph II alternatively, the total drag of the eight-car group train reduces by up to 4.6% and 1.8%, respectively, while the drag reduction can be up to 6.3% with deflectors installed in both pantograph I and II areas. This paper can provide references for the aerodynamic design of a new generation of highspeed trains.