【作者】 汪孛；

【导师】 谷正气；

【作者基本信息】 湖南大学 ， 车辆工程， 2010， 硕士

【摘要】 近年来,我国公路的建设日新月异,公路交通运输的水平得到了很大的发展。集装箱运输货车作为公路运输的主要工具,发挥着越来越重要的作用。为了提高运输效率,适应日益严格的节能减排政策以及促进环保,货车的空气动力学越来越受到人们的重视。风洞试验和数值模拟是目前研究汽车空气动力学气动特性的主要研究方法。随着计算机技术的发展以及成本等因素的考虑,计算流体力学(Computational Fluid Dynamics,简称CFD)方法被越来越多的应用到汽车的开发过程中。本文介绍了汽车空气动力学发展历史和研究现状以及计算流体力学在汽车上的发展和应用状况。采用CFD方法对集装箱货车外流场进行研究,数值计算结果对于货车的设计与开发具有一定的指导意义。首先,在集装箱货车三维CAD模型的基础上建立网格计算模型,运用CFD软件Fluent对货车在无侧风下行驶的外流场计算模拟。通过对集装箱货车外流场的流态进行详细分析研究,探讨了集装箱货车外流场的流动特征和气动阻力之间的关系,明确了产生气动阻力的主要原因,为后续减阻提供了参考依据。接着,运用试验设计方法选取若干组试验点,基于响应面模型的基础上,建立起阻力系数和升力系数与导流罩几何参数之间的数学函数关系,利用优化算法对阻力系数函数得出最优解,与CFD数值模拟结果相比较,误差在5%以内。结合敏感性分析,分析出对整车气动阻力影响较为敏感的结构参数,对某款商用导流罩进行气动优化设计,对实车中的导流罩设计具有指导意义。随后,讨论了三种横摆角下数值模拟汽车的方法,基于标模的基础上与风洞试验对比。经比较分析,本文选用方法3对集装箱货车进行横摆角下数值模拟。最后,根据集装箱货车外流绕流特点,在集装箱前部加装涡流扰流装置,并探讨了该扰流装置几何参数对整车气动阻力的影响,为提升侧风环境中集装箱运输货车气动阻力特性水平提供了参考依据。更多还原

【Abstract】 With the rapid progress on the construction of expressway in our country, the road transportation has great development.Nowadays,container semi-trailer truck, as the major tool in road transportation, plays an increasingly important role.To improve the efficiency of transportation, adapt the stricter policies on energy-saving and emission reduction, it is paid more and more attentions on the truck aerodynamics.There are two major methods used in vehicle aerodynamics,which are wind tunnel test and numerical simulation. With the rapid development of computer technology and taking the cost into consideration, the method of Computational Fluid Dynamics (CFD) is more and more widely applied to the process of automobile’s research and development.It is reviewed that the developing history and the current situation on road vehicle aerodynamics and CFD.The external field of the truck was simulated by the CFD method. The result of numerical simulation provides an instruction for the truck design and research.At first, generate the grid computational model on the basis of three dimensional CAD model of the truck. Numerically simulate the external field of the truck without crosswind making use of the CFD software Fluent.The air flow in the external field of the truck is analytical researched in detail.The relationship between the flow characteristic of external flow field of the truck and the aerodynamic drag is on discussion.The reason why the drag was produced is clear. It provides references for the following work of drag reduction.The next, select several experimental points using Design of Experiment (DOE), based on the Response Surface Method (RSM),the function relationship is established between coefficient of drag and lift and the five parameters,which reflect the cab roof fairing.The optimization solution can be obtained by algorithm.To compare with the result of CFD numerical simulation, the relative error is less than 5%.Combined with the sensitivity anlysis,analyze the structural parameters which are sisitive to the aerodynamic drag of the truck.Optimizing design for a kind of commercial cab roof fairing,it has the guiding sense to the cab roof fairing of the real truck.Furthermore,three methods of simulating the truck in yaw angles were discussed. To compare with the result of wind tunnel test based on the standard model,method 3 was used for simulating the truck in yaw angles in this paper.At last,based on the truck aerodynamic characteristic of external flow, the vortex trapped device added on the front of the trailer. The influence on the aerodynamic drag by the geometric parameters of that was discussed.It provides references that improving the characteristic of drag of the truck in crosswind.更多还原