Research On Aerodynamic Characteristics And Driving Stability Of Vehicles In Overtaking Process

With the rapid development of the automobile industry and the rapid construction of highways,the traffic volume of highways has continued to increase,and the safety of automobiles in overtaking has also received widespread attention.As one car passes another during an overtaking maneuver at a high speed,the external flow fields between the two cars will interfere with each other,affecting the aerodynamic forces acting on the body,and then adversely affecting the driving stability and safety of the car.Therefore,the research on the aerodynamic characteristics and driving stability of the car during the high-speed overtaking maneuver has important theoretical guidance and engineering application value for improving the safety of the car.Aiming at this problem,a two-way coupled analysis method of computational fluid dynamics and multi-body dynamics was used to investigate the aerodynamic characteristics and dynamic response of the car during overtaking,and the effects of relative velocity and road adhesion conditions on the overtaking maneuver were also explored.Firstly,a computational fluid dynamics model was established using dynamic mesh technology to simulate the overtaking maneuver,which was used to calculate the transient aerodynamic loads of the car during overtaking.The accuracy of the numerical model was verified by wind tunnel tests.Meanwhile,in order to capture the car’s dynamic response to external disturbances,a multi-body dynamic model of the car including aerodynamic loads and road input was established,and a robust test was performed to verify the model.Secondly,a joint simulation platform for two-way coupled analysis of computational fluid dynamics and multibody dynamics was established,and the driving stability simulation experiments were performed using one-way and two-way coupled methods.By comparing the simulation results,the accuracy and necessity of the bidirectional coupling calculation method are verified.Then,a two-way coupling analysis method was used to simulate the overtaking maneuver,and the interaction between the car’s motion response and its aerodynamic loads was explored.The changes of aerodynamic characteristics during overtaking were analyzed from three aspects: aerodynamic load change,key position flow field and body pressure distribution.Moreover,based on the analysis of the body’s dynamic response and driving trajectory,the movement of the overtaking car during the overtaking maneuver was summarized.The results show that when the overtaking car completely exceeds the overtaken car,the driving stability of the overtaking car is the worst,and the possibility of a collision between two cars is also the greatest.Finally,the comparative simulations of the overtaking maneuver in different conditions was conducted to explore the effects of relative velocity and road adhesion coefficient on the aerodynamic characteristics and dynamic response of the overtaking car.The results show that increasing the relative velocity will reduce the stability of the overtaking car,but also reduce the possibility of collision with the overtaken car.On a low-adhesion road,the overtaking car has worse stability and is more likely to collide with the overtaken car,which is a very dangerous driving condition.