【作者】 张苗；

【导师】 胡广洪； 范秦寅；

【作者基本信息】 上海交通大学 ， 材料加工工程， 2011， 硕士

【摘要】 伴随着机械制造技术的快速发展和高速公路数量的提高,汽车高速行驶的时间比率大大增加;同时随着汽车保有量的飞速提高,汽车在路面上的行驶工况也越来越复杂,经常会出现超车、会车、队列行驶等情况。当汽车在高速超车时,车身周围流场不断急剧变化,车身周围的空气流场间也产生强烈的气动干扰,致使车辆所受的六分力不断的变化,进而造成车辆发生偏移和转移,严重影响车辆行驶时的稳定和安全。我国每年高速公路碰撞事故中与高速超车有关的占很大比例,给国家和人民的生命财产带来了极大的损失。因此研究汽车高速超车过程中的空气动力学特性具有非常重要的意义。国际上对汽车直道超车过程的空气动力学特性一直十分重视,但是针对变道超车过程的空气动力学特性的研究还尚未展开。到目前为止,已经先后有很多家知名大学和研究机构应用CFD模拟方法对直道超车过程进行了仿真分析,但大部分CFD模拟方法都采用的是不连续网格方法。本文基于Ahmed汽车简化模型,采用重叠网格和不连续网格两种方法分别对直道超车过程的外部流场进行了数值仿真。通过比较在此过程中的主超车与被超车的阻力系数、升力系数的变化规律以及车身表面压强系数分布情况,验证了重叠网格应用于超车过程外部流场数值仿真上的适用性和准确性。并分析了重叠网格方法的计算原理和目前存在的问题,提出了解决此问题的方法。在此基础上,本文进一步的开创性的应用重叠网格方法实现了变道超车过程的外部流场数值仿真,通过分析主超车与被超车的阻力系数、升力系数、侧向力系数的关系与变化规律,揭示了在变道超车过程中,两车外部流场相互干扰作用的变化规律。本文通过以上计算和分析,指出了重叠网格方法在汽车外流场仿真模拟方面的潜力,并为解决实际车型的变道超车等问题提出了简便实用的方法,具有一般指导意义。更多还原

【Abstract】 With the rapid development of mechanical manufacturing technology and increase of the numbers of highways, the time of high-speed running has been greatly increased and the driving conditions become more complex. When the cars are overtaking at a high speed, the flow fields around the car body will change constantly and produce a strong aerodynamic interference. It will result the constant changing of the six-pitch forces and cause shifts of vehicles, which seriously affect the stability and security of the vehicles. The annual collisions of automotive have a large proportion of overtaking with a high speed in china. Therefore, the research of aerodynamic characteristics during the high speed overtaking is very important and meaningful.Many famous universities and research institutes have finished the calculation and simulation of overtaking by CFD (Computational Fluid Dynamics) analysis process, but so far the most of the CFD calculation methods are based on discontinuous mesh method. The overset mesh and discontinuous mesh will be used respectively on the numerical simulation of the external flow field of overtaking in line based on the Ahmed model. In this process, the applicability and accuracy of overset mesh method in simulating the automotive external flow field are proved by comparing the variation of the aerodynamic coefficient and the distribution of body surface pressure. The principle and the problems of the calculation of the overset mesh method are pointed out, and the solving ways are analyzing too.Thus, the overset mesh method is used to finish the numerical simulation of the external flow field of overtaking by switching lines for the first time. The variation law of the aerodynamic interference is researched by the analysis of the variation of the aerodynamic coefficient and the effects to the safety are analyzed.These calculations show the potential of the overset mesh method to solve the problems such as overtaking by switching lines and provide a way to solve such problems of the actual vehicles.更多还原