【作者】 向活跃；

【导师】 李永乐；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 随着列车高速化与轻量化的发展,强横风作用下列车的安全性问题越来越突出。在线路一侧或两侧设置风屏障,为列车创造一个相对低风速的局部环境,是提高列车横风安全性的有效措施。围绕铁路风屏障的防风效果及其自身风荷载,采用理论分析、风洞试验及数值模拟的方法,进行了如下研究：首先,通过风洞试验,研究了圆孔式风屏障缩尺模型中孔径的合理取值,对比了风屏障开孔形式以及圆孔式风屏障与格栅式风屏障的相似性。在同一网格条件下,采用CFD方法研究了风屏障的直接模拟方法和多孔介质方法,并与风洞试验结果进行了对比。在风洞试验基础上,进一步对车辆的雷诺数效应、风场分布、车辆风荷载及车辆动态响应等方面进行了研究。车辆雷诺数效应方面,结合数值模拟方法得到了车辆气动力系数随雷诺数变化的曲线,除雷诺数突变区域和过渡区域外,阻力系数满足指数律,并进一步分析了车辆的升阻比与车顶的流动状态关系。风场分布方面,测试了轨道上方的风压系数剖面,分析了气动机理。车辆风荷载方面,分析了风屏障高度与透风率、车辆位置、双车交会及线路构造形式等因素的影响,讨论了铁路风屏障的升力机理,即气流绕过一定高度的风屏障后,减小了轨道上方的平均风速,同时会加速并形成强剪切层,当其经过曲线车顶时,增加了车顶的局部雷诺数,使得风屏障对车顶和车底的防风效果有一定差异,导致车辆升阻比增加,并有可能增加升力系数。车辆动态响应方面,采用风-车-桥耦合振动分析方法,对比了设置风屏障时车辆的动态响应。其次,提出了横向风作用下高速运动车辆气动力系数的理论关系式,分析了理论关系式中各项系数的物理意义,通过文献中的试验数据验证了其可靠性。基于风屏障阻力机理及Baker假定,结合上述理论关系式,提出了设置风屏障时运动车辆气动特性的近似计算公式,采用CFD对其进行了验证。在此基础上,提出了沿平地路基运行的尾车的附加气动作用计算公式,在多种透风率风屏障情况下进行CFD验证,并进一步研究了线路构造形式的影响。再次,通过风洞试验,研究了不同高度、不同透风率、不同线路构造形式情况下,风屏障在横向风作用下的自身风荷载。完善了列车风作用下风屏障风荷载峰值随距离变化的经验公式,采用数值模拟方法对其进行了验证,并讨论了风屏障位置、透风率及车速等因素的影响。为决定是否在风屏障性的综合评价中考虑瞬态风荷载的影响,针对实际工程,建立了风屏障的有限元模型,分析了列车风作用下风屏障的疲劳特性。最后,根据车辆气动力系数的含义以及风洞试验结果,提出以单车时的气动力系数衡量车辆的风载突变效应。分别以车辆的风荷载突变量及车辆的动态响应为输入指标,在输出指标相同情况下,采用数据包络法(DEA)对风屏障性能进行了综合评价,并讨论了车辆风荷载指标与车辆响应指标间的一致性。结果表明：横风作用下运动列车的气动特性由运动项、静止项及边界项组成,设置风屏障具有相似的规律。风屏障的防风作用是阻力机理与升力机理联合作用的结果,以阻力机理为基础的近似计算方法在预测车辆的侧向阻力系数时效果较好,升力系数和侧滚力矩系数稍差。线路构造形式对轨道上方的风场分布、静止车辆风荷载、运动车辆风荷载、车辆走行性及横风作用下的风屏障风荷载的影响较大。列车风作用下,风屏障的瞬态风荷载随距离的增加而迅速减小,实际风屏障的应力幅较小。综合评价结果表明,平地路基上风屏障透风率为0%、高度为2.95m(轨面以上高度为2.05m)时防风效果较好,车辆风载突变效应和车辆响应指标间的一致性较好。更多还原

【Abstract】 With the development of high-speed and light-weight of trains, the security of the train becomes a problem of increasing concern. In order to create a local environment which has a relatively lower wind speed for trains, the wind barriers either one side or both sides are installed on the railway, which is an effective measurement to protect the trains from the strong cross wind. Therefore, in this study, the method of theory analysis, wind tunnel tests and numerical simulations are used to investigate the protection effects of railway wind barrier and its wind loads.Firstly, the wind tunnel tests are conducted to investigate the reasonable aperture of circle-hole wind barrier in scaled model, and study the similarity between circle-hole wind barriers with grid wind barriers. Under the condition of the same grid, the wind barriers are simulated by the boundary of wall and porous jump in FLUENT, and compare to the results of wind tunnel tests. Based on wind tunnel tests, the effects of Reynolds number of vehicles, wind field distribution, vehicle wind loads, and vehicle dynamic responses are studied. In the aspect of the vehicle Reynolds number, the curves of the aerodynamic force coefficients to Re are obtained by the numerical simulation method, and it shows that the drag coefficient satisfies the exponential law except for the sudden change region and transition region; furthermore, the relationship between the lift-drag ratio of vehicle and the flow pattern of the vehicle roof are discussed. In the aspect of wind field distribution, the profiles of wind pressure coefficient above track are measured by wind tunnel tests, and the aerodynamic mechanism is analyzed. In the aspect of vehicle wind loads, the height and porosity of wind barriers, track positions, and two trains meeting each other et al. are discussed, and the lift mechanism of railway wind barrier is proposed, i.e. after the airflow bypassing the wind barriers with certain height, the accelerated airflow (strong shear layer) will act on the roof of the vehicle, consequently, increase the local Reynolds number of vehicle roof, and lead to some differences of protection effect of wind barriers between the vehicle roof and bottom, which increase the lift-drag ratio of vehicle, and also may be increased the lift coefficient. In the aspect of vehicle dynamic responses, the coupled vibrations of wind-vehicle-bridge system method are adopted to calculate the dynamic responses when the wind barriers installed on the railway.Secondly, a theoretical relationship of moving vehicle aerodynamic force coefficient under the cross wind is proposed, and the physical meanings of theoretical relationship are analyzed; meanwhile, the reliability is verified by the experimental data in literature. In terms of the wind barrier drag mechanism, Baker’s hypothesis and the theoretical relationship, an approximate calculation formula of moving vehicle aerodynamic characteristics when the wind barriers are installed on one side is proposed, and it be verified by CFD. On this basis, a formula of additional aerodynamic force effect is suggested, which is only suitable for the last vehicle running on the ground roadbed, and it be verified by CFD in the multiple wind barrier cases. Further, the applicability of theoretical relationship, the approximate calculation formula, and the additional aerodynamic action in the different line structure forms are studied by CFD method.Thirdly, the cross wind loads of wind barriers are measured by wind tunnel tests, and the effect of height, porosity, and line structure forms are discussed. Furthermore, under the action of train-induced wind, the empirical fitting formula of the peak drag coefficients for wind barrier changed with distance is proposed, which is verified by numerical simulation method, the effects of distance, porosity, and vehicle speeds on the drag coefficient of wind barrier are discussed respectively. A finite element model of wind barrier is used to analyze the stress distribution, and the fatigue characteristics of wind barrier under the action of train-induced wind are further analyzed to determine whether the transient wind load will be considered as an evaluation index.Finally, in terms of the definition of vehicle aerodynamic force coefficients and the results of wind tunnel tests, it is presented that the effect of sudden change of vehicle wind loads can be measured by aerodynamic force coefficients of the single train. Because of the output indexes are the same, the magnitudes of sudden change of vehicle wind loads, and the vehicle dynamic responses are considered as the input indexes, respectively, and the method of DEA (Data Envelopment Analysis) is used to evaluate the performance of wind barrier. According to the evaluation results of wind load and vehicle response, the consistency between the index of wind loads and the index of responses are discussed.The results demonstrated as follows:the aerodynamic characteristics of moving vehicles under the cross wind were consisted of the movement item, static item, and boundary item, When the wind barrier installed the railway, the aerodynamic characteristic is also satisfied this theoretical relationship. The protection effect of wind barrier was the result of the combination effects of drag mechanism and lift mechanism, the lateral drag coefficient when the wind barrier installed on the railway could be better estimated by the approximate calculation method based on the drag mechanism, but the lift coefficient and side roll moment coefficient were somewhat less compared with CFD. The line structure forms had significantly effect on the wind field distribution, wind load of static vehicle and moving vehicle, and wind load of wind barrier under the cross wind. Under the action of train-induced wind, the transient wind loads of wind barrier decreased rapidly with the increasing of wind barrier distance, which led to a smaller stress range for the practical wind barrier. When the porosity is0%, the height is2.05m (the height above the track plane), the protection effect of wind barriers installed on ground roadbed was better, and the sudden change of vehicle wind loads was in good agreement with the vehicle response index.更多还原