Mingzhi Yang

Moving Model Test of High-Speed Train Aerodynamic Drag Based on Stagnation Pressure Measurements

A moving model test method based on stagnation pressure measurements is proposed to measure the train aerodynamic drag coefficient. Because the front tip of a high-speed train has a high pressure area and because a stagnation point occurs in the center of this region, the pressure of the stagnation point is equal to the dynamic pressure of the sensor tube based on the obtained train velocity. The first derivation of the train velocity is taken to calculate the acceleration of the train model ejected by the moving model system without additional power. According to Newton’s second law, the aerodynamic drag coefficient can be resolved through many tests at different train speeds selected within a relatively narrow range. Comparisons are conducted with wind tunnel tests and numerical simulations, and good agreement is obtained, with differences of less than 6.1%. Therefore, the moving model test method proposed in this paper is feasible and reliable.

A new moving model test method for the measurement of aerodynamic drag coefficient of high-speed trains based on machine vision

A moving model test method has been proposed to measure the aerodynamic drag coefficient of a high-speed train based on machine vision technology. The total resistance can be expressed as the track friction resistance and the aerodynamic drag according to Davis equation. Cameras are set on one side of the track to capture the pictures of the train, from which the line marks on the side surface of the train are extracted and analyzed to calculate the speed and acceleration of the train. According to Newton’s second law, the aerodynamic drag coefficient can be resolved through multiple tests at different train speeds. Comparisons are carried out with the full-scale coasting test, wind tunnel test, and numerical simulation; good agreement is obtained between the moving model test and the full-scale field coasting test with difference within 1.51%, which verifies that the method proposed in this paper is feasible and reliable. This method can accurately simulate the relative movement between the train, air, and ground. The non-contact measurement characteristic will increase the test accuracy, providing a new experimental method for the aerodynamic measurement.

Research on the Influence of Shaft Area on Alleviating Tunnel Aerodynamic Effects Through Dynamic Model Test

Series of compression waves and expansion waves caused by EMUs entering tennels at high speed will give rise to a series of tunnel aerodynamic effects: excessive pressure change will not only has effect on the fatigue life of EMU bodies and subsidiary structures in tunnels but also endangers the riding comfort of passengers. In addition, tunnel micro-pressure waves can even cause noise which effect the surrouding environment. Installing ventilation shafts inside tunnels is helpful to alleviate tunnel aerodynamic effects and the area of ventilation shaft is an important parameter. Dynamic model test system in Central South University was used in this paper to test and analyze the compression waves and expansion waves caused by trains entering tunnels and micro-pressure waves formed at tunnel exit, and to compare the influence of shaft with different area on the pressure change inside tunnel, the pressure change on train surface and the micro-pressure wave amplitudes. Test results show that the pressure changes inside tunnel and on train surface can be reduced effectively when the shaft area is 10% of the tunnel area; The larger the shaft area is, the smaller the tunnel micro-pressure amplitude will be.