In Crosswind-Bridge Pylon Environment Research On Automotive Aerodynamic Characteristics With CFD-MBD Dynamic Coupling Method

The process of the automobile passing through the bridge pylon area is a typical driving condition.When automobile enters or exits the bridge pylon area in a crosswind environment,the complex and changeable wind environment causes the causes change of aerodynamic force suddenly.This force could easily cause the automobile to slip and yaw,affecting the stability of the automobile and leading to serious accidents.Therefore,it is of great practical significance to study the aerodynamic characteristics of the automobile under the crosswind-bridge pylon environment.The main contents of this thesis were as follows:(1)The history and current situation of experimental and numerical simulation researches on automobile aerodynamic characteristics were expounded.The research status of the influence of the wind environment in the bridge pylon area on the aerodynamic characteristics of the automobile was discussed.(2)The STAR-CCM+ was used to design the automobile aerodynamic numerical simulation model.The aerodynamics of the aerodynamic at different yaw angles was verified through wind tunnel experiments.The Adams/car was used to design the automotive multibody dynamics model.The robustness of the automobile multi-body dynamics model was verified by changing the point of action of the lateral force and calculating the corresponding automobile dynamic response.(3)A dynamic coupling method based on automotive aerodynamics and automotive multibody dynamics was proposed and compared with the static coupling method.For the same working condition,the static and dynamic coupling methods were used for calculation.The differences between the aerodynamic force,flow field,and dynamic response of the automotive calculated by these two methods were discussed.The aerodynamic characteristics and dynamic response of the automotive under crosswind environment were analyzed,and the necessity of applying the dynamic coupling method was explored.(4)The dynamic coupling method was used to study the influence of the wind environment on the aerodynamic characteristics of the automotive from the aspects of aerodynamics,flow field,and dynamic response.The effects of step,linear and sinusoidal crosswinds on the aerodynamic characteristics of the automobile were analyzed.The aerodynamic characteristics of the automobile in the crosswind-bridge pylon environment were explored.The results of this thesis were as follows: The dynamic coupling method was designed considering the feedback effect of automobile motion on the flow field.The method was then compared with the static coupling method.The aerodynamic force and dynamic response of the automobile calculated by the dynamic coupling method were smaller.Its calculation results were more in line with the actual situation.Therefore,it was necessary to carry out a dynamic coupling analysis on the aerodynamic characteristics of the automobile in a crosswind environment.As the automobile passes through the wake area of the bridge pylon,the values of lateral force and yaw moment decrease sharply at first and increase rapidly afterwards.The dynamic coupling method realistically simulated the interaction between the shedding vortex in the wake region of the bridge pylon and the flow field around the automobile.The aerodynamic force and dynamic response of the automobile in the step,linear and sinusoidal crosswind environment were compared.According to the analysis results,the risk for automobile encountering step crosswind environment was the highest.