Numerical calculation of the slipstream generated by a CRH2 high-speed train

Slipstreams caused by high-speed train movement through the atmosphere pose a safety risk to passengers, trackside workers and track infrastructure. The improved delayed detached eddy simulation (IDDES) approach, an improved version of the detached eddy simulation method, is adopted in this paper to calculate the slipstream of a four-coach 1/25th-scale model of the CRH2 high-speed train. Slipstream velocities and pressures at various lateral distances from the centre of rail (COR) position and vertical distances from the top of rail (TOR) position at trackside are calculated. Numerical results are compared with measurements obtained in a full-scale test and good agreement is obtained, which verifies the effectiveness and potential of the less costly IDDES method. It is found that the velocity and pressure distributions are similar to those obtained using different train types but with different peak values related to the difference in shapes. The peak velocities in the slipstream along the length of the train are found at the tail and in the near wake region. The magnitude of the peak decreases with an increasing distance from the COR and shows a relatively high value at about two thirds of the train height from the TOR. The maximum pressure coefficients are found in the upstream and nose regions. The results show that the value of these coefficients decreases with an increasing distance from the COR and TOR. Based on the suggested safe slipstream velocity in China, the IDDES results show that for a CRH2 high-speed train at a speed of 350 km/h, the safe standing distance should be greater than 3.4 m in the lower part of the train's slipstream (up to about half of the train height from the ground) and 2.4 m for the top part of the train's slipstream (above half the height of the train from the ground).