RESEARCH ON TURBULENT BOUNDARY LAYER OF HIGH-SPEED TRAINS

In recent years, developments of highway and air transport have produced great impact on the railway transportation, high-speed railway becomes a kind of trend. High-speed railway is complicated system engineering, and many factors which can be ignored in low speed become important factors of safety to the high speed train. The characteristics of boundary layer influence the aerodynamic performance of the train sharply. According to the characteristics of the engineering, this paper calculated the performance parameters of the turbulent boundary layer of incompressible fluid by different geometric models of high-speed trains, compared the different results due to the full model, half model and simplified model, and fully discussed the influence of the calculation models in analyzing the turbulent boundary layer of high-speed train. Results using the half train model and simplified model satisfy the laws of turbulent boundary layer, however, the numerical simulation results and the accuracy would be impacted. The high-speed train model is simplified, the boundary layer thickness of the top and the side is decreased, the air flow distribution around the middle train and the end train is significantly improved; also the resistance coefficient and the pressure drag coefficient are decreased. Using the half train model has great impact on the velocity distribution around and end the train, the resistance and shear stress coefficient are bigger and the boundary layer thickness is smaller. A lot of resources could be saved by using half model, and accurate flow field data in the core area could be got, however, the issue of boundary layer should be used cautiously.