Feasibility of replacing the 3-coach with a 1.5-coach grouping train model in wind tunnel experiment at different yaw angles

The effects of different yaw angles on the aerodynamic performance of city electric multiple units (EMUs) were investigated in a wind tunnel using a 1:16.8 scaled model. Pressure scanning valve and six-component box-type aerodynamic balance were used to test the pressure distribution and aerodynamic force of the head car respectively from the 1.5- and 3-coach grouping city EMU models. Meanwhile, the effects of the yaw angles on the pressure distribution of the streamlined head as well as the aerodynamic forces of the train were analyzed. The experimental results showed that the pressure coefficient was the smallest at the maximum slope of the main shape-line. The side force coefficient and pressure coefficient along the head car cross-section were most affected by crosswind when the yaw angle was 55 degrees, and replacing a 3-coach grouping with a 1.5-coach grouping had obvious advantages for wind tunnel testing when the yaw angle was within 24.2 degrees. In addition, the relative errors of lift coefficient C-L, roll moment coefficient C-Mx, side force coefficient C-S, and drag coefficient C-D between the 1.5- and 3-coach cases were below 5.95%, which all met the requirements of the experimental accuracy.