Structure Clearance Design in Wind Tunnel Tests with Implications for Aerodynamic Drag of High-Speed Trains

The influences of vestibule diaphragm gap, wheel-rail clearance, and strut-plate gap on the aerodynamic drag of a 1/8th-scale high-speed train model were investigated in an 8 m×6 m wind tunnel. The Reynolds number was set to 2.2×10 6 based on train height. It was found that the variation of the vestibule diaphragm gap changed the aerodynamic drag distribution pattern of each car; the drag coefficient of the head and middle cars might change as high as 45%; however, the change in the drag coefficient of the total train was very small. The effects of the strut-plate gap on the aerodynamic drag of each car and the total train were small. The effect of the wheel-rail clearance on the drag of the head car was not significant. It was suggested that the vestibule diaphragm gap, strut-plate gap and wheel-rail clearance of the 1:8 scale high-speed train model should not be greater than 11, 10, and 9 mm, respectively.