The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains. Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph. However, less attention has been paid to the pantograph recess compared with the pantograph. In this paper, the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess, which is represented as a rectangular cavity and numerically investigated at 1/10 scale. Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation, and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction. The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications, and consequently, the noise radiated from the cavity is reduced. Furthermore, effects of the rounded cavity edges on the flow and noise of the pantographs (one raised and one folded) are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges. Different train running directions are also considered. Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph, whereas the flow velocity in the cavity is slightly increased by the rounding. Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph, whereas weaker fluctuations are found on the panhead of the raised pantograph. This study shows that by rounding the cavity edges, a reduction in radiated noise at the side and the top receiver positions can be achieved. Noise reductions in the other directions can also be found.

中文翻译：

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腔流量控制对高速列车受电弓和车顶空气动力噪声的影响

受电弓及其在车顶上的凹槽是高速列车上主要的空气动力学噪声源。减少这种噪声尤为重要，因为常规的噪声屏障通常不会屏蔽集电弓。但是，与受电弓相比，对受电弓凹部的关注较少。在本文中，针对简化的高速火车受电弓凹部（以矩形空腔表示并以1/10比例进行了数值研究），研究了圆形和倒角两种类型的降噪处理的流动特征和噪声贡献。对近场湍流模拟进行了改进的延迟分离涡模拟，并将Ffowcs Williams和Hawkings航空声比拟用于远场噪声预测。通过腔边缘的修改，大大降低了腔上高度不稳定的流动，因此，减少了从腔辐射的噪声。此外，通过比较带和不带腔边缘的情况下的流动特征和噪声贡献，研究了圆形腔边缘对受电弓的流动和噪声的影响（一个凸起和一个折叠）。还考虑了不同的火车行驶方向。流动分析表明，通过使空腔边缘变圆，可以减少空腔内高度不稳定的流动，并且在凸起的集电弓的上部周围会出现稍低的流速，而通过变圆，空腔中的流速会稍微增加。折叠的缩放仪和升高的缩放仪的下部会出现较高的压力波动，而在凸起的受电弓的云台上发现的波动较小。这项研究表明，通过使腔体边缘变圆，可以减少侧面和顶部接收器位置的辐射噪声。也可以找到其他方向的降噪效果。