沟槽微结构尺寸对高速列车横风特性影响研究

Influence of groove microstructures on the aerodynamic performance of high speed trains under crosswind

随着列车运行速度的不断提升,气动效应对列车运行安全性产生的影响越来越突出。目前针对高速列车横风效应的研究通常假定列车表面光滑,实际上列车表面是非光滑的,边界层内的流动特性有所不同。利用微结构进行非光滑表面设计的新型技术手段可能改善高速列车在横风条件下的气动性能。以在车顶加设矩形条带组的方式,对1∶25比例的列车模型进行局部非光滑设计;采用改进的延迟分离涡模拟(IDDES)方法对横风作用下光滑表面和粗糙表面的列车模型进行气动性能模拟。结果表明,与光滑模型相比,粗糙模型下的侧向力系数和倾覆力矩系数分别降低了3.71%和10.56%。选取条带的宽度、高度和长度为设计变量,基于正交试验设计方法设计不同的数值模拟方案,利用方差分析和极差的方法探索矩形条带几何参数与列车侧向力和倾覆力矩间的关系,给出条带外形设计的优选方案。本研究可为横风作用下如何提升高速列车的气动性能提供理论依据。

With the continuous improvement of train speeds,the influence of aerodynamics on the train safety is increasingly prominent.Especially,the crosswind will significantly deteriorate the aerodynamic performance of high-speed trains and bring greater security risks consequently.Present research regarding the crosswind effect on high-speed trains usually assumes that the train surface is smooth,which is,however,not true.Non-smooth surfaces with microstructures will change the flow characteristics in the boundary layer and may improve the aerodynamic performance of high-speed trains.The present study uses an improved delayed detached eddy simulation(IDDES)method was used to obtain the aerodynamic performance of 1∶25 scale train models with smooth and rough surfaces under crosswind.The non-smooth surface is achieved by adding a group of rectangular strips on the top of the train model.The results show that the side force coefficient and the roll moment coefficient can be respectively reduced by 3.71%and 10.56%by using a non-smooth surface.The width,height,and length of the strip are selected as design variables,and different numerical simulation schemes are designed based on the orthogonal experimental design method.The relationship between the geometric parameters of rectangular strip and the side force coefficient and roll moment coefficient of the train is explored by the variance and range analyses,and the optimized strip shape is given.This study can hopefully provide a theoretical basis for the improvement of aerodynamic performance of high-speed trains under crosswind.