高速列车近尾流区涡旋结构的湍流特性分析

Analysis on Turbulence Characteristics of Vortex Structure in Near Wake of High Speed Train

为降低高速列车的气动阻力和气动噪声提供理论支撑,以CRH380A型高速列车为原型,建立比例尺为1∶30的高速列车空气动力学模型,应用分离涡模拟方法对其周围流场进行数值计算。在对数值模拟方法合理性验证的基础上,结合湍动能和雷诺应力的变化规律,对高速列车近尾流区涡旋结构的湍流特性进行分析。结果表明:在尾车鼻端附近,近尾流区涡旋结构中的湍流涡旋具有可观的湍动能,并随着向下游发展而逐渐耗散,与此同时涡旋结构中所携带的能量沿展向方向移动;在尾车鼻端附近,受车体侧表面分离形成的剪切流动的影响,近尾流区涡旋结构中的湍流涡旋在较高的垂向位置上能够使流向和展向的脉动速度之间保持很好的相关性,而离尾车稍远的湍流涡旋则会在较低的垂向位置产生相对较大的雷诺应力;雷诺应力在垂向上的变化规律受到分别来自车体底部和车体顶部的分离剪切流动的影响,并且尾车鼻端附近的湍流涡旋在受到由车体底部分离形成的剪切流动的作用时,能使流向与垂向的脉动速度之间保持相对较好的相关性,即相应的雷诺应力较大。

In the attempt to provide theoretical support for lowering the aerodynamic drag and noise of high speed train, an aerodynamic train model at 1 ： 30 scale was established based on the CRH380A high speed train, and the flow field around the model was calculated numerically using detached eddy simulation. On the basis of verifying the rationality of numerical simulation method, according to the curves of turbulent kinetic energy and Reynolds stress components, analyses were made on the turbulence characteristics of vortex structure in the near wake of high speed train. Results show that, near the nose of the trailing car, those turbulent vortices of the near wake vortex structure possess considerable turbulent kinetic energy that is gradually dissipated when propagating downstream along the streamwise direction, meanwhile the energy has to be carried by the vortex structure and transferred in the spanwise direction. When influenced by the shear flow separated from the sides of the model, near the nose of the trailing car, the turbulent vortices of the near wake vortex structure can maintain good correlation between the streamwise and span- wise fluctuating velocities at the higher vertical position, while those vortices slightly far from the tail are able to generate comparatively large Reynolds stress values at the lower vertical position. It is also found that the Reynolds stress variations along the vertical direction result from the separated shear flows sepa- rately from the bottom and roof of the model. Furthermore, the streamwise and vertical fluctuating veloci- ties can be better correlated to each other, namely the corresponding Reynolds stress component has larger values, near the nose where the turbulent vortices are significantly influenced by the shear flow separated from the model bottom region.