Research On Aerodynamic Characteristics Of Lane Change Overtaking Based On CFD

With the development of China’s high-grade highways and the increase in car ownership,the driving conditions of cars on the expressway are becoming more and more complicated,and there is often a phenomenon of lane change.When the car is driving at high speed,the high-speed airflow interacts with the car body,and its external flow field directly affects the economy,power,steering stability and driving safety of the vehicle.The mutual interference between the two vehicles outside the lane change process leads to a change in the aerodynamic force of the vehicle,which causes the vehicle body to vibrate,affects the operational stability and driving safety of the vehicle,and endangers road traffic safety.The annual traffic accidents on expressways in China account for a large proportion of accidents related to overtaking,which seriously affects the safety of people’s lives and property.Therefore,this paper will apply the dynamic grid technology in CFD software to numerically simulate the lane changing process and explore the lane change.During the overtaking process,the change of the flow field outside the two vehicles and the change process of the vortex explain the reasons for the change of the vehicle aerodynamic force.This paper optimizes the car model used for lane changeover,starting from the simplification of the original model,to geometric patching,model zoning,generating surface meshes,to building computational domains,dividing volume meshes,setting boundary conditions,and physical models for cars.The model performs a steady state simulation.The vehicle model is analyzed by the surface pressure distribution map,the symmetry plane velocity vector diagram and the isosurface map with the total pressure coefficient of 0.The aerodynamic optimization scheme is developed,and the optimal optimization scheme is combined to obtain the optimal drag coefficient value.Compared with the original model.the drag coefficient of the model is reduced by 0.07,and the vortex area at the tail of the model is improved significantly.Based on the optimized vehicle model,the lane change analysis is carried out.Using the dynamic grid technology,the profile changeover process is realized by importing the profile file,and the pressure cloud map,velocity vector diagram,streamline diagram and lateral force change trend are analyzed and will change.The change of the flow field outside the two vehicles at different positions during the overtaking process and the change process of the bound vortex and free vortex in the flow field are combined with the changes of the force state of the two vehicles.The comprehensive analysis provides theoretical suggestions for the driving of the car.Design the lane change overtaking simulation with different speeds and different spacings,and compare them at the same position during the overtaking process:as the absolute speed increases,the lateral forces of the two vehicles are increased,which is affected by overtaking.Compared with the main overtaking,it is more significant;as the overtaking distance increases,the lateral forces of the two vehicles are reduced,and the impact of the main overtaking is more obvious than that of the overtaking.The numerical simulation of the overtaking of different models is carried out.Compared with the same model,the overtaking process of the lane change shows that the lateral forces of the two vehicles are increased during the lane change of different models.The variation curve of the lateral force of the two vehicles shows that the trolley is subject to the following:The impact is more significant than that of the big car;during the overtaking of different models,the bound vortex and free vorticity and motion amplitude of the two external flow fields are more significant,and the energy in the flow field is consumed a lot,for the two cars.The impact of the force state is more significant.