Comparative Analysis of Surface Pressure Fluctuations of High-Speed Train Running in Open-Field and Tunnel Using LES and Wavenumber-Frequency Analysis

Abstract

The interior noise of a high-speed train due to the external flow disturbance is more than ever a major problem for product developers to consider during a design state. Since the external surface pressure field induces wall panel vibration of a high-speed train, which in turn generates the interior sound, the first step for low interior noise design is to characterize the surface pressure fluctuations due to external disturbance. In this study, the external flow field of a high-speed train cruising at a speed of 300 km/h in open-field and tunnel are numerically investigated using high-resolution compressible LES (large eddy simulation) techniques, with a focus on characterizing fluctuating surface pressure field according to surrounding conditions of the cruising train, i.e., open-field and tunnel. First, compressible LES schemes with high-resolution grids were employed to accurately predict the exterior flow and acoustic fields around a high-speed train simultaneously. Then, the predicted fluctuating pressure field on the wall panel surface of a train was decomposed into incompressible and compressible ones using the wavenumber-frequency transform, given that the incompressible pressure wave induced by the turbulent eddies within the boundary layer is transported approximately at the mean flow and the compressible pressure wave propagated at the vector sum of the sound speed and the mean flow velocity. Lastly, the power levels due to each pressure field were computed and compared between open-field and tunnel. It was found that there is no significant difference in the power levels of incompressible surface pressure fluctuations between the two cases. However, the decomposed compressible one in the tunnel case is higher by about 2~10 dB than in the open-field case. This result reveals that the increased interior sound of the high-speed train running in a tunnel is due to the compressible surface pressure field.

Interior noise prediction of inter-coach space of high-speed maglev trains based on wavenumber decomposition on aerodynamic excitation

“…Additionally, sound reflections may significantly increase the magnitude of AWPF. 23 As high-speed maglev lines are generally routed in areas where buildings are sparsely spaced, sound reflections from sound barriers and surrounding buildings are not considered in this paper.

Figure 1.Computational model. (a) Computational domain.

…”

“…In recent years, with the development of computational fluid dynamics (CFD) and computational aeroacoustics (CAA), many attempts have been made to model transmission path and to predict interior noise. Attention has been already paid to the influence of acoustic pressure components on interior sound pressure level (SPL) in several studies regarding automobiles and high-speed trains, and the main areas of concern included front side window and rearview mirror of cars, 8,9,[17][18][19][20] pantograph platform 21 and side wall 22,23 of high-speed trains, etc. However, interior SPL prediction of high-speed maglev trains on the basis of different transmission paths, to the best of our knowledge, has not yet been published.…”