The external windshield is a key component in high-speed trains for drag reduction. However, the installation gap between external windshields, which is intended for improving curve-passing ability, could lead to strong aerodynamic instability in train-end area and therefore significant operating risk for train. This study aims to advance this field based on detailed numerical simulation, investigating the related flow features in this area, particularly from a time-dependent perspective. Flow field around external windshields with different installation gaps (10, 20 and 30 mm) is resolved based on Improved Delayed Detached Eddy Simulation (IDDES). The aerodynamic forces on different windshield components, turbulent flow fields around the train-end area, and corresponding low-dimensional modes are analyzed. The results show that the difference in the external windshield gap can significantly affect the related aerodynamic forces, with the 20 mm case having the highest time-averaged values. The aerodynamic spectrum shows primary, secondary and tertiary peak frequencies with a relatively high power spectral density (PSD). Decreasing the gap distance generally increases the overall PSD in the Strouhal number ranges considered, particularly for the secondary and tertiary peaks. The load forms and their energy distributions under different external windshield gaps are obtained through the proper orthogonal decomposition analysis.

外挡风玻璃是高速列车减阻的关键部件。但是，为了提高弯道通过能力，外挡风玻璃之间的安装间隙可能导致列车末端区域的空气动力不稳定，从而给列车带来很大的运行风险。本研究旨在基于详细的数值模拟推进该领域，研究该领域的相关流动特征，特别是从时间相关的角度。基于改进的延迟分离涡模拟 (IDDES) 解决了具有不同安装间隙（10、20 和 30 mm）的外部挡风玻璃周围的流场。分析了不同挡风玻璃部件上的气动力、列车末端区域周围的湍流场以及相应的低维模态。结果表明，外部挡风玻璃间隙的差异会显着影响相关的气动力，其中 20 mm 的情况下具有最高的时间平均值。空气动力学频谱显示具有相对较高的功率谱密度 (PSD) 的主要、次要和三次峰值频率。减小间隙距离通常会增加所考虑的 Strouhal 数范围内的整体 PSD，特别是对于二级和三级峰。通过适当的正交分解分析得到不同外挡风玻璃间隙下的载荷形式及其能量分布。具有相对较高的功率谱密度 (PSD) 的二次和三次峰值频率。减小间隙距离通常会增加所考虑的 Strouhal 数范围内的整体 PSD，特别是对于二级和三级峰。通过适当的正交分解分析得到不同外挡风玻璃间隙下的载荷形式及其能量分布。具有相对较高的功率谱密度 (PSD) 的二次和三次峰值频率。减小间隙距离通常会增加所考虑的 Strouhal 数范围内的整体 PSD，特别是对于二级和三级峰。通过适当的正交分解分析得到不同外挡风玻璃间隙下的载荷形式及其能量分布。