侧风环境中车辆出隧道过程的气动特性研究

发布时间：2018-01-14 19:03

本文关键词：侧风环境中车辆出隧道过程的气动特性研究　出处：《山东大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着我国公路通车里程的逐年增加以及汽车保有量的迅速增长,我国正快速进入汽车社会。我国各种地势地貌相当复杂,特别是以山区居多,山地和丘陵占居全国总面积的三分之二以上。为保证道路的连续性和合理性,经常采用建设隧道来穿越山岭。近年来,我国公路隧道通车里程和座数逐年增多。我国为多风国家,当车辆由隧道内驶出时,由于车辆是由相对封闭的空间进入开放空间,汽车本身的空气动力学特性会发生很大的变化,加之受到风的影响,汽车的侧倾力会急剧变化,导致失控和侧翻等交通事故。另外,在实际道路行驶时,车辆不可避免的会发生跟随以及并行,此时车身周围气流的会发生变化,从而带来车辆行驶安全问题。本文采用基于动态分层法的动网格技术对侧风环境中车辆驶出隧道过程的气动特性进行研究,分析所涉及的流动现象和力学结果之间的关系并且得出相应的结论。具体如下：首先对单辆货车驶出隧道的过程进行数值计算,将计算结果与前人实验值及稳态数值模拟的结果进行对比,计算结果误差在允许范围内,为后续的数值模拟提供了依据和保证。研究单辆货车驶出隧道过程的气动特性,设置4种不同的行驶速度以及4种不同的风速进行对比分析。发现货车在驶出隧道后其阻力系数变小,且侧风速度越大时,货车驶出隧道后的阻力系数越大,其侧向力系数也越大。货车的气动力系数在隧道出口前后发生了较大的波动,且侧风速度越大,货车周围的流速及压力分布越不均匀,其气动力系数波动越大,行驶安全性越差。研究侧风状态下两辆车相互尾随出隧道时两车的气动特性,将车速设置为30m/s,设置4种不同的侧风速度,引入标准轿车模型并变换轿车和货车的前后位置进行对比分析。发现两车相互尾随时前后两车的阻力系数均有一定程度的减小,且前车车型大时后车阻力系数减小的幅度也大。前车的尾涡对后车有一定的影响,使后车的气动力系数发生波动,且前车车型大后车车型小时前车对后车的影响最为明显,前车车型小后车车型大时,后车受前车影响较小。研究侧风状态下两辆车并行驶出隧道时两车的气动特性,同样固定车速,设置4种不同的侧风速度,并变换迎风侧的车型进行对比分析。发现两货车并行时左右两车的阻力系数的值和变化趋势基本一致,在无侧风时左右两车的侧向力系数绝对值基本相等,但侧向力方向相反,有侧风时左边背风侧货车的侧向力系数绝对值小于右边迎风侧,且左边货车的切向力系数与阻力系数的比值小于1,说明右车对侧风有一定的屏蔽作用。轿车在右边迎风侧货车在左背风侧时,两车的阻力系数变化趋势一致,无侧风时两车的侧向力方向相反,大小基本一致,随着侧风速度的增加左右两车的侧向力系数均有所增加,但左边货车的增加幅度减小,且左边货车切向力系数与阻力系数的比值大于1,说明小轿车对侧风有一定的屏蔽作用,但由于迎风面积较小,所以该作用表现不明显。货车在右边迎风侧轿车在左边背风侧时,由于货车迎风面积较大,对侧风的屏蔽作用大,导致小轿车的侧向力系数绝对值很小且切向力系数与阻力系数的比值小于1,气动力系数波动明显。本文探讨了车辆在侧风下驶出隧道时的气动特性规律,从空气动力学的角度解释了隧道出口多发生交通事故的原因,为有风天气时车辆在隧道的安全行驶提供了理论依据。
[Abstract]:With the rapid growth of China's highway mileage has increased year by year, the amount of automobile, China has quickly entered the automobile society. China's various terrain topography is very complex, especially in the mountainous areas are mountainous and hilly country occupies more than 2/3 of the total area of the road. In order to ensure the rationality and continuity, are often used in tunnel construction to pass through the mountains. In recent years, China's highway tunnel traffic mileage and seat number increased year by year. China's wind state, when the vehicle is in the tunnel exit, because the vehicle is composed of a relatively closed space into the open space, the aerodynamic characteristics of vehicle itself will change a lot, and affected by the wind roll, the car will change sharply, resulting in loss of control and rollover accidents. In addition, in the real road, the vehicle will inevitably occur following and parallel, the body around the gas The flow will change, leading to the safety of the vehicle. The dynamic characteristics of dynamic mesh technique and dynamic layering method of vehicle crosswind in the process of gas out of the tunnel based on study, the relationship between the flow phenomena and mechanical results involved and draw the corresponding conclusion. As follows: firstly, the process of truck out of the tunnel and the numerical calculation, the numerical simulation results and experimental values and the steady-state results were compared, the results error is in the allowable range, provide the basis and guarantee for the subsequent study. Numerical simulation of a truck out of the tunnel of the aerodynamic characteristics of 4 different speed and 4 different wind speed were analyzed. Found the truck pulled out of the tunnel in after the drag coefficient is smaller, and the crosswind velocity is large, the truck pulled out after the tunnel resistance coefficient is Large, the lateral force coefficient is large. The aerodynamic coefficients of trucks have biggish fluctuation at the tunnel exit before and after, and the greater the crosswind velocity, flow velocity and pressure distribution of the truck around the less uniform, the aerodynamic coefficients of larger fluctuation, the driving safety is worse. Of two cars are under crosswind conditions trailing out of the tunnel when the two car aerodynamic characteristics, the speed will be set to 30m/s, set 4 different crosswind velocity, introducing a standard car model and transform the cars and trucks of front and rear position were analyzed. Two reduced vehicle tail at any time before and after the two car drag coefficient to a certain extent, and the first car models when the car drag coefficient reduced greatly. The wake before the car has certain effect on the car, the car's aerodynamic coefficients after fluctuations, and before the car car after the car before the car vehicle hour effect on the car is the most obvious, the vehicle in front of the car After the small car models when the car is less affected by the car. Study under crosswind conditions of two cars and two cars running out of the tunnel when the aerodynamic characteristics of the same fixed speed, setting 4 different crosswind velocity, and transform the windward side models are compared and analyzed. It is found that the drag force coefficients of two trucks in parallel about two of the car value and is basically the same trend. The lateral force coefficient about two car in side wind the absolute value is basically the same, but the lateral force in the opposite direction, with side wind coefficient of lateral force left the leeward side of the absolute value of less than truck on the right and left the windward side, the vehicle tangential force coefficient and resistance ratio the coefficient is less than 1, indicating the right car has a shielding effect on the car on the right side. The crosswind windward truck on the leeward side left, two car drag coefficient of the same trend, no side wind side force two cars in the opposite direction, the size is consistent with. The increase of lateral force coefficient increased about two with crosswind speed of the car, but the increase of the left truck decreases, and the ratio of tangential force coefficient and vehicle drag coefficient is greater than 1, indicating the car has a shielding effect on crosswind, but because the windward area smaller, so the effect is not obvious. In the van the car on the left side of the leeward side of the windward side, as the truck windward area is larger, the shielding effect of the crosswind, leading to lateral force coefficient of the absolute value of the car is very small and the ratio of tangential force coefficient and drag coefficient is less than 1, the aerodynamic coefficient fluctuates significantly. This paper discusses the dynamic characteristics of vehicle driving under cross wind tunnel when the gas, explains why many traffic accidents occurred in the tunnel exit from the angle of aerodynamics, as wind weather vehicle in the tunnel driving safety provides a theoretical basis.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U461.1

【相似文献】