Numerical Simulation Study On The Process Of A Car Overtaking A Tractor-Trailer Truck

In recent years with the rapid development of automobile industry,the performances of vehicle including motor vehicle dynamic characteristics, fuel economy, handing directional stability, traveling comfort, safety efficiency are greatly concerned with consumer. In addition, not only traffic accidents of highway are greatly increasing, but also the laypeople and the vehicles on the road are. Based on the above reasons, vehicle automatic drive, intelligent drive and the performance requirements of traffic safety become the essential and indispensable component of automobile and transportation research. However, automobile aerodynamics is closely bound up with these topics. Meanwhile, numerical computation of aerodynamics is widely applied with the progress of computer, large quantities of relative paper has been presented. But at present, the relative literature about turbulence characteristics of plural vehicles running in row and passing maneuvers is very limited. Pointing to the above difficulty, in this paper, numerical computation of turbulent-velocity field is studied while a sedan exceeding a tractor-trailer truck. From the vehicle safety angle, it provides theory and technical support for the research on automatic drive, intelligent drive and traffic safety.This paper is based on the study of single car external flow field about the simulation on the ground boundary layer, the rotating wheels and the crossing wind load, and on the two cars running-in-row and overtaking maneuvers. The simulation methods and content about the mesh generation, the boundary condition of rotating wheels and moving ground of single car, and about the steady study on the two car running in row and overtaking process has shown the calculation results reliability and the numerical simulation methods feasibility. Based on the comparison and analysis of mesh strategy, the Descartes mesh strategy and the tetrahedron + prism mesh strategy are chosen. The continuous unsteady overtaking process of the vehicles, traveling with constant but unequal speed is replaced by a finite numerber of steps; in each the relative position of both vehicles changes. Ten typical longitudinal relative and two vehicles are selected to simulate the overtaking process and study the aerodynamic interference characteristics. Based on the ten relative positions of the two vehicles, the domain of computational meshes and boundary conditions of every position are set, and the RNG k-εturbulence model and Simple difference scheme are chosen. The study on the process of a home-made sedan overtaking a tractor-trailer truck is carried on STAR-CD platform. The convergent results are obtained. The comparisons of aerodynamic forces coefficients and the y plus distribution on the two vehicles surface have shown the better mesh strategy's results.