The flow and flow-induced noise behaviour of a simplified high-speed train bogie in the cavity with and without a fairing

Abstract

Aerodynamic noise is a significant source for high-speed trains but its prediction in an industrial context is difficult to achieve. In this article, the flow and aerodynamic noise behaviour of a simplified high-speed train bogie at scale 1:10 are studied through numerical simulations. The bogie is situated in a cavity beneath the train and the influence of a bogie fairing on the flow and flow-induced noise that developed around the bogie area is investigated. A two-stage hybrid method is used, which combines the computational fluid dynamics and an acoustic analogy. The near-field unsteady flow is obtained by solving the unsteady three-dimensional Navier–Stokes equations numerically using delayed detached-eddy simulation, and the data are utilised to predict the far-field noise based on the Ffowcs Williams–Hawkings acoustic analogy. Results show that when the bogie is located inside the bogie cavity, the shear layer developed from the leading edges of the cavity interacts strongly with the flow separated from the upstream components of the bogie and the cavity walls. Therefore, a highly turbulent flow is generated within the bogie cavity due to the strong flow impingements and flow recirculations occurring there. For the case without the fairing, the surface shape discontinuity in the bogie cavity along the carbody sidewalls generates strong flow unsteadiness around these regions. When the fairing is mounted in front of the bogie cavity, the flow interactions between the bogie cavity and the outer region are reduced and the development of turbulence outside the fairing is greatly weakened. Based on the predictions of the noise radiated to the trackside using a permeable data surface parallel to the carbody sidewall, it has been found that the bogie fairing is effective in reducing the noise generated in most of the frequency range, and a noise reduction of around 5 dB is achieved in the farfield for the current model case.