Study on the pressure pipe length in train aerodynamic tests and its applications in crosswinds

The pressure integral method is frequently used to obtain the train aerodynamic forces in experiments, but the effect of the pressure pipe length on the pressure amplitude is not understood. In this paper, based on field tests without pressure pipes, the dominant frequency (DF) ranges of the pressure pulsations on the train surface under various conditions, including open-air, crosswind, and tunnel conditions, were analyzed. Then the effect of the pressure pipe length on the pressure amplitude with various pulsation frequencies was investigated. Finally, in a full-scale test under crosswinds, the selected pressure pipe length was applied to verify its reliability and to study the train aerodynamic performance. The results showed that the maximum DF occurred when two trains passed each other (near 60 Hz), and the DF under crosswinds was the smallest (less than 1 Hz). When the pressure pulsation frequency was less than 1 Hz, the error range of the pressure amplitude was less than 5% with a pressure pipe length of ≤8 m. The pressure pipe is a polyvinyl chloride (PVC) pipe with an outer diameter of 2 mm and an inner diameter of 1.8 mm. The full-scale test results for the windproof ability of different windbreak walls and the aerodynamic forces of the train showed that the current pressure pipe length was reasonable and could reflect the actual operating conditions of the train under crosswinds.