列车绕流的瞬态与稳态数值模拟对比

Comparison of unsteady and steady simulations of the flow around trains

采用大涡模拟(Large Eddy Simulation,LES)和基于雷诺平均(Reynolds Average Navier_Stocks,RANS)的SST(Shear Stress Transport)k_ω湍流模型,分别对高速列车单车明线运行进行瞬态和稳态的仿真计算,通过与实车测试数据比较对数值模拟进行了验证.对比分析LES和RANS的计算结果发现:对于车头表面测压点,LES和RANS都能给出高精度的计算结果,且LES的瞬态计算结果表明,表面压力最大值在一个很宽的范围内波动;对于列车绕流结构,LES较RANS表现出更强的小尺度涡的捕捉能力,尤其表现在复杂的尾流区;通过气动力系数的傅里叶变换分析了波动的频域特性.LES在较复杂列车模型外流场模拟中的高计算精度,及其广泛的结果信息可以为列车的系统耦合设计提供可靠的数据参考.

The air flow around high-speed trains is usually defined as three-dimensional, unsteady tur- bulent, for which the transient characteristics are important. Large Eddy Simulation （LES） and Reynolds Average Navier-Stockes （RANS） with SST（Shear Stress Transport） k-ω turbulent model were used to perform the transient and steady simulations, respectively and the results were verified with full-scale experimental data. Comparison results of LES and RANS show that they both give ac- curate results for the tapping pressure points on the head of the train. The transient results of LES indi- cate that the maximum surface pressure fluctuates in a wide range. LES shows more reliable ability in capturing the small scale vortex structure than RAINS with regard to visualizing the flow structure, es- pecially in the wake flow. High accuracy of LES method in aerodynamic simulations under slightly complex train model, as well as its comprehensive results can provide reliable reference for the coupling system design of the train.