###### Abstract  
The high-speed-train pantograph is a complex structure that consists of different rod-shaped and rectangular surfaces. Flow phenomena around the pantograph are complicated and can cause a large proportion of aerodynamic noise, which is one of the main aerodynamic noise sources of a high-speed train. Therefore, better understanding of aerodynamic noise characteristics is needed. In this study, the large eddy simulation (LES) coupled with the acoustic finite element method (FEM) is applied to analyze aerodynamic noise characteristics of a high-speed train with a pantograph installed on different configurations of the roof base, i.e. flush and sunken surfaces. Numerical results are presented in terms of acoustic pressure spectra and distributions of aerodynamic noise in near-field and far-field regions under up- and down-pantograph as well as flushed and sunken pantograph base conditions. The results show that the pantograph with the sunken base configuration provides better aerodynamic noise performances when compared to that with the flush base configuration. The noise induced by the down-pantograph is higher than that by the up-pantograph under the same condition under the pantograph shape and opening direction selected in this paper. The results also indicate that, in general, the directivity of the noise induced by the down-pantograph with sunken base configuration is slighter than that with the flush configuration. However, for the up-pantograph, the directivity is close to each other in Y-Z or X-Z plane whether it is under flush or sunken roof base condition. However, the sunken installation is still conducive to the noise environment on both sides of the track. high-speed train; pantograph; aerodynamic noise; large eddy simulation; acoustic finite element method +
Footnote †: journal: Applied Soft  
trains cause serious aerodynamic noise pollution to passengers and surroundings. [PERSON] (2016) indicated that aerodynamic noise becomes a main pollution source when train speed exceeds 250-300 km/h. His results indicated that, with the increase of train speed, the noise increases rapidly and the aerodynamic noise almost increases with the sixth power of the train speed. To date, the aerodynamic noise characteristics of high-speed trains have been investigated numerically and experimentally. Based on numerical approaches, aero-acoustic analysis is applied to simplified and real-oriented high-speed train geometries to evaluate aerodynamic noise. The numerical approaches could be divided into direct and hybrid methods. The direct methods commonly use the direct numerical simulation (DNS), large eddy simulation (LES), or detached eddy simulation (DES) to simulate the flow field and aerodynamic noise simultaneously. In this kind of methods, the grid scale and energy capture requirements differ between the analysis of the flow field and the analysis of the acoustic propagation. It is found that the magnitude of sound pressure is smaller when compared to that of the dynamic pressure in the flow field. The direct methods are required to adopt high-order, low-dissipation, low-dispersion discretization schemes to produce appropriately accurate solutions ([PERSON] and [PERSON], 2016). Moreover, since the shape of high-speed trains is rather complex, the use of the direct methods can suffer from high computational costs. Consequently, the hybrid methods seem at present more attractive for practical engineering problems. In the hybrid methods, sound sources in the near field and sound propagation in the far field are solved separately. The pressure fluctuations are solved using a high-order technique of LES, DES or are modeled from turbulence statistics obtained from Reynolds Average Navier-Stokes (RANS) simulations. Then, the pressure fluctuations are analyzed by means of acoustic methods to solve the acoustic propagation. Presently, the trend of the research on the aerodynamic noise of high-speed trains is mostly based on the hybrid methods.