For high-speed trains the aerodynamic noise sources become important for speeds above about 300 km/h. The pantograph is mounted on the train roof, often in a shallow cavity. Because of its elevated position it is an important source of noise from high-speed trains, especially in the presence of noise barriers which shield sources that are lower on the train. In this paper, the flow features and noise sources of a high-speed train pantograph and its recess are numerically investigated at a speed of 300 km/h (Mach number 0.24). The geometry of the pantograph recess is simplified as a 'closed' rectangular cavity and two pantographs (one opened and one retracted) are included that are based on a DSA 350 pantograph. To resolve the details of the turbulent flow structures and hence enable accurate noise predictions, the Improved Delayed Detached-Eddy (IDDES) model is used to model the flow field. The Ffowcs-Williams & Hawkings aeroacoustics model is employed for far-field acoustic calculations. In comparison with the same cavity without pantographs, the flow around the cavity shows slightly different characteristics when the pantographs are placed in the cavity. The wake region in the downstream region of the cavity is slightly reduced due to interaction between cavity flow and pantographs. This can affect the noise emission from this region. This study indicates that the main noise sources are from the raised pantograph, and the panhead of the retracted pantograph as shear layers impinge on them. The cavity trailing edge also generates significant levels of noise. The far-field noise is found to be broadband. The directivity of the noise radiated from pantographs and cavity is also obtained.

中文翻译：

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空腔流动对高速列车受电弓气动噪声影响的数值研究

对于高速列车，空气动力噪声源在速度超过约 300 公里/小时时变得很重要。受电弓安装在火车车顶上，通常在一个浅腔中。由于其较高的位置，它是高速列车的重要噪声源，尤其是在存在屏蔽列车上较低噪声源的隔音屏障的情况下。本文对高速列车受电弓及其凹槽在300km/h（马赫数0.24）时的流动特征和噪声源进行了数值研究。受电弓凹槽的几何形状被简化为一个“封闭”的矩形腔体，包括两个基于 DSA 350 受电弓的受电弓（一个打开，一个缩回）。为了解决湍流结构的细节，从而实现准确的噪声预测，改进的延迟分离涡流 (IDDES) 模型用于模拟流场。Ffowcs-Williams & Hawkings 气动声学模型用于远场声学计算。与没有受电弓的同一腔体相比，当受电弓放置在腔体中时，腔体周围的流动表现出略有不同的特性。由于腔流和受电弓之间的相互作用，腔下游区域的尾流区域略有减少。这会影响该区域的噪声发射。本研究表明，主要噪声源来自升高的受电​​弓和缩回的受电弓的盘头，因为剪切层撞击它们。腔体后缘也会产生大量噪声。发现远场噪声是宽带的。