Abstract:
In order to explore the influence of tail-blowing control on the aerodynamic resistance of urban rail trains, the DDES method based on realizable
k-
ε two-equation model is used to simulate the flow structures around the train body on open railways, and the numerical method is verified by wind tunnel test results. The influence of the tail-blowing control at different positions and different blowing speeds is analyzed. The results show that, the pressure drag is an important source of the train resistance, accounting for about 80.1% of the total resistance, while the friction drag accounts for about 19.9%. The air blowing control can significantly reduce the aerodynamic resistance of the train, with much greater influence on the pressure drag than the friction drag. Under different air blowing schemes, the drag reduction effect on the rear car is most significant, followed by the middle car, with the highest drag reduction rates of 27.6% and 4.6%, respectively. The pressure in the separation area and the strength of the streamwise vorticity are important factors affecting the train resistance. When the blowing boundary is close to the core of the streamwise vortex, the streamwise vorticity is weakened. When the blowing speed increases from 0.2
U to 0.4
U, the drag reduction rate increases from 7.9% to 12.2%. When the blowing speed further increases to 0.6
U, the drag reduction effect weakens, with the overall drag reduction rate reaching 12.9%. The wake structure varies with the angle between the blowing direction and the wall tangential direction. When the central blowing point increases from 1.5 m to 5.0 m from the nose tip of the tail car, the aerodynamic drag reduction rate of the train decreases from 12.9% to 11.3%.