The flow and flow-induced noise behaviour of a simplified high-speed train bogie in a cavity and including a fairing

Aerodynamic noise is a significant source for high-speed trains but its prediction in an industrial context is difficult to achieve. The flow and aerodynamic noise behaviour of a simplified high-speed train bogie at scale 1:10 are studied here 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 developed around the bogie area is investigated. A two-stage hybrid method is used, combining 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 utilized 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 cavity leading edge interacts strongly with the flow separated from the bogie upstream components 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 side walls 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 predictions of the noise radiated to the trackside using a permeable data surface parallel to the carbody side wall, it is found that the bogie fairing is effective in reducing the noise generated in most of the frequency range and a noise reduction around 5 dB is achieved in the farfield for the current model case