Computer Simulation Of Passing An Automobile And Research Upon Its Effect On Aerodynamic Character

It is a very common phenomenon that an automobile is passed by another one on the road. That mainly includes overtaking and head-on passing. Due to the interference of flow stream in passing an automobile, pressure distributions which can produces transient aerodynamic force is formed and makes change quickly during this course. So automobile will automatically make some unpredictable actions such as roll, yaw and so on, which gives great threaten to safe driving. This thesis researches the aerodynamic character in passing an automobile.Different from past assumption about ideal state of single automobile, there exists relative stream more than two. It is difficult to study with traditional method. With the development of computer fluid dynamic (CFD), CFD technology is more and more used in the design and development of automobile. This thesis applies CFD to research change of aerodynamic character in overtaking and head-on passing.Firstly, this thesis researches on the aerodynamic character of automobile and analyses its effect on driving stability from three aspects such as side force and jaw moment, lift force and pitch moment, roll moment. This thesis yet deeply discusses effect of disturbed flow on driving stability.Secondly, two kinds of turbulence model widely used in automobile aerodynamics are introduced and applied respectively to simulate external flow field of a sedan. A comparison is given based on the computation result.Before the application of commercial CFD software, a very important work is to evaluate credibility of the software. This thesis uses the method of comparison between experiment result and computation result to complete this work.At last, this thesis uses method of subsection simulation to simulate overtaking and on-head passing and analyses effect of passing an automobile on aerodynamic character. Considering the diversity of automobile on the road, this thesis builds three types of full-scale numerical model of automobile: hatchback, sedan and container trailer. From three aspects that lateral space, relative velocity and relative volume, this thesis studies effect of passing an automobile on aerodynamic character and gives conclusion based on the computation result.