Research On The Automobile Aerodynamic Character Of High Speed In Complicated Traffic

In complicated traffic driving at high speed includes three states—overtaking,head-on passing and trailing.Since in such situation,the surrounding flow fields of the body and instantaneous distribution of pressure are changing rapidly,it is easy to cause some unexpected conducts such as roll,yaw,flutter and so on,bringing threats to driving stability and economy of petrol.With these factors concerned,this thesis carries out a research on aerodynamic character of high speed in complicated traffic.Driving at high speed in complicated traffic is different from the situation where a single car is running in the ideal circumstance,because the comparatively complicated flow field would make the traditional research methods impossible.With the development of Computational Fluid Dynamics(CFD),this thesis firstly employs moving mesh to simulate the states of overtaking,head-on passing and trailing respectively,and analyzes the aerodynamic character of driving at high speed in complicated traffic.A research on aerodynamic character of cars is launched here,and discussions are emphasized on the influence of disorder flow on driving during actual running.Then some common two-equation turbulence such as k-εmodel,RNGk-εmodel are briefly introduced,and after scientific comparison and analysis this thesis adopts RNGk-εmodel to simulate.Then there is a brief introduction of the commercial software STARCD,followed by a detailed introduction of basic theory of moving mesh.In light of the driving variety in complicated traffic,the thesis develops the numerical modes separately—model of cars and model of trucks.In the last part,employing moving mesh,the thesis describes the simulation of the complicated states of overtaking,head-on passing and trailing,and then analyzes their influence on aerodynamic character.The simulation of overtaking and head-on passing mainly focuses on the aspects of lateral space,relative velocity and models of autos,and the influence on the car's aerodynamic character in the situation of the car trailing the trunk is primarily discussed.Based on the result of simulation,the thesis analyzes the changing rules of aerodynamic character and a study on their effect on running stability and petrol economy is followed.