Experimental and Numerical Study of the Flow Field Structure of High-Speed Train with Different Nose Lengths Head at 15° Yaw

Abstract

By using three different head types (5 m, 7.5 m and 10 m nose lengths), the CRH3 (China Railway High-speed 3) flow field structure at 15° yaw was studied through wind tunnel experiments and numerical simulations. The modifications of the aerodynamic coefficients were studied using the Improved Delayed Separation Eddy Simulation (IDDES) method. The results show that the longer the nose length of the tail car, the more it is affected by crosswind. However, the increase in turbulence mitigates the risk of overturning the tail car as the pressure distribution between the train side surface and the underbody becomes more disturbed. The nose length of the head car can affect the position and length of the longitudinal vortex core on the leeward side, thus affecting the lift and side force of each section of the train. The location of the time-averaged vortex core for a 15° crosswind is approximately 0.67H~0.7H high from the ground and 0.65H~0.67H wide from the center of the train. The main frequency of the leeward vortex ranges from 0.1 to 0.3. The transient vibration amplitude at the position of the vortex core is the largest, and the main frequency of vibration is 0.18. The tail car nose length should be properly lengthened since increasing the length of the tail car reduces the negative pressure on the surface of the tail car, thus reducing drag and side force. However, the excessive length of the tail car nose increases the risk of overturning under crosswind.

Keywords

• nose lengths
• leeward longitudinal vortices
• PIV
• high-speed train