【作者】 杨滨徽；

【导师】 谷正气；

【作者基本信息】 湖南大学 ， 车辆工程， 2010， 硕士

【摘要】 汽车空气动力学特性是车身造型设计的前提基础和理论依据,它会影响到汽车的动力性、操纵稳定性、安全性、经济性、乘员的舒适性和周围环境等多个方面,是评价整车性能的重要指标,并已经成为汽车能否在激烈的市场竞争中取胜的重要因素。随着我国汽车产业和高等级公路的迅速发展,汽车车速不断提高,汽车空气动力学研究在国内倍受关注。随着国内汽车空气动力学研究不断深入发展,汽车外流场的研究不再局限于对简单的理想型体或其他简化模型的稳态分析,对接近实车的几何形体和瞬态问题的研究受到越来越多的关注。新的研究领域呈现出内外流场相互耦合、复杂工况与复杂环境相互耦合等多因素偶合的特征。由于风洞试验的局限性,CFD技术在这些新的领域中发挥着越来越重要的作用。本文以国家创新工程“中气计划”为平台,开展了隧道内复杂工况下汽车高速气动特性研究工作,将轨道交通中的压力波研究引入到汽车空气动力学特性研究中来,数值计算结果对于中气轿车设计与开发有一定的实际指导意义。首先本文对Ahmed模型、中气轿车、隧道进行了六面体网格划分,根据网格节点和单元的编号,编写了网格变化子程序。然后运用滑移交界面(Sliding Interface)和移动网格(Moving Mesh)技术实现网格的移动来对Ahmed外流场进行了瞬态数值模拟。并对比了其稳态流场的压力分布、湍动能、湍流粘性、速度标量,分析了二者的差别以及产生这些差别的原因。最后运用滑移交界面和移动网格技术对单车过隧道、隧道内轿车与轿车迎面会车、隧道内轿车超轿车的外流场进行了数值模拟,找出这些复杂状态下轿车车身压力波、气动力的变化规律,并分析了其原因。更多还原

【Abstract】 Automotive aerodynamic characteristic is the principal and theoretical basis for the automobile body design.It affects vehicle dynamic characteristic,driving stability,security, economy,comfort and environment.It has been an important indicator to evaluate automobile performance.It takes an important role for automobile to win the fierce market competition. With the rapid progress on the development of domesic automotive industry and expressway,it is paid more and more attention on the automotive aerodynamic.As the research on automotive aerodynamic get further, the focus of external flow field research is going to shift from simple modle and steady analysis to real model and unsteady analysis.New reseach field has the characteristics coupling muti-factors. Beacause of the limitation of wind tunnel test,CFD (computational fluid dynamic) is more and more widely applied in new research fields.Subsidized by national innovation project"zhongqi program",aerodynamic characteristic of high speed vehicles in tunnel is on disscution,the result of numerical simulation can provide an instruction for the car design and research.Before the numerical analysis, the hexa mesh of ahmed model, car and tunnel model are created.It takes almost half workload of whole thesis.Then write the program changing mesh.Next,with sliding interface and moving mesh technique provided by STAR-CD software,the transit external flow field around ahmed model is simulated.Compared with the pressure,turbulent kinetic energy,turbulent viscosity,velocity magnitude distribution from steady anlysis,the difference between transit result and steady result is concluded.At last, with sliding interface and moving mesh technique,the 3-D transient external flow field when single vehicle go through tunnel,two vehicles pass each other and one automobile overtake another in tunnel are simulated.The tendency of changing drag and side force is provided.By analyzing the pressure distribution and velocity vector on some sections,pressure pulse on some cells,the reason for the tendency and transient aerodynamic characteristics are concluded.更多还原