Key Takeaways & Executive Findings
- •• The flow-through cowcatcher suppresses flow separation and promotes stable vortex evolution in the bogie cavity, reducing high-amplitude wall pressure fluctuations by up to 40%. • Far-field sound pressure levels decrease by 0.4–0.6 dB(A) with the flow-through cowcatcher, as validated by semi-anechoic wind tunnel experiments. • The dominant sound source around the leading bogie region is shrunk with intensity reduced by about 1.0 dB(A), confirming effective aerodynamic noise mitigation. • The study provides theoretical insight and engineering guidance for low-noise design of high-speed train nose cars.
Abstract
This study introduces a novel flow-through cowcatcher with integrated inlet and outlet channels as an aerodynamic noise mitigation strategy for the nose car of a high-speed train. The wall-adapting local eddy-viscosity large-eddy simulation (WALE-LES) combined with the Ffowcs Williams-Hawkings (FW-H) acoustic analogy approach is employed to evaluate its impact on the aerodynamic and aeroacoustic characteristics of the leading bogie region. Compared with the conventional closed cowcatcher, results show that the flow-through structure suppresses the flow separation, promotes more stable vortex evolution within the bogie cavity, and reduces the spatial extent of high-amplitude wall pressure fluctuations up to 40%, mitigating effectively the generation of aerodynamic noise. Semi-anechoic wind tunnel experiments validate the simulation results and demonstrate that the sound pressure levels at the far-field observers decrease by 0.4 −0.6 dB(A) with the flow-through cowcatcher applied underneath the nose car. The dominant sound source around the leading bogie region is shrunk with intensity reduced about 1.0 dB(A). These findings confirm the effectiveness of the flow-through cowcatcher in reducing the aerodynamic noise produced from the leading bogie region, providing both theoretical insight and engineering guidance for structural optimization and low-noise design of the nose car in a high-speed train.
1. Introduction
With the continuous increase in the operating speed of high-speed trains, aerodynamic noise has become a dominant component of the overall noise profile. When the train speed exceeds 300 km/h, the traditional primary sound source—wheel-rail rolling noise—gradually gives way to aerodynamic noise [1]. Among the various regions of the train, the leading bogie area beneath the nose car is particularly prone to aerodynamic noise due to its complex structure and intense flow disturbances [2]. This region features multiple geometric discontinuities such as bogie frames, wheelsets, and underbody cavities, which readily induce strong shear layers, vortex shedding, and large-scale unsteady flow structures under high-speed conditions. These flow phenomena cause strong wall pressure fluctuations and the flow-induced noise is generated and radiated.
During recent years, increasing attention has been paid to understand the mechanism of aerodynamic noise generated from bogie regions. LIANG et al [3] used the large-eddy simulation (LES) to reveal the mechanisms of flow separation and vortex evolution and identified that flow-structure interaction was a key aerodynamic sound source. LATORRE et al [4] conducted wind tunnel experiments on a 1:7 scaled train-bogie model and found that components exposed to the oncoming flow, such as motor boxes, wheelsets, and dampers, were dominant noise contributors, whereas shielded internal parts had lesser impact. HUANG et al [5] performed a three-dimensional numerical simulation of the leading bogie using LES model and Ffowcs Williams-Hawkings (FW-H) approach, showing that the noise was broadband with no distinct dominant frequencies, with A-weighted sound pressure levels (SPLs) primarily between 315 Hz and 1250 Hz. LAN et al [6] further examined the correlation between pressure fluctuations and acoustic radiation, confirming the significance of coherent structures within the cavity.
Recent advancements in modeling fidelity have provided deeper insight into the spatial and spectral characteristics of bogie noise. ZHAO et al [7] applied the improved delayed detached-eddy simulation (IDDES) method in a train-cutting-wind scenario, showing that deeper cuttings enhanced the flow blockage, leading to a more stable flow field and mitigated aerodynamic fluctuations after the train entered. The abrupt aerodynamic load on the leading car increased nearly linearly with wind speed. LU et al [8] performed a scale-sensitive study of bogie flow and aerodynamic noise using LES and finite element methods across four geometric scales. They found that feedback disturbances within the bogie cavity were tightly coupled with the surrounding shear flow, and that scaling affected both the dominant frequency content and source distribution. As the model size decreased, the noise energy shifted to higher frequencies and the contributions from structural elements like the rear
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CHENG Guan-da, ZHU Jian-yue, ZHU Tai-hang, PANG Jia-bin, FANG Cun-yu (2025). Behaviours of flow and flow-induced noise generated from leading bogie region of high-speed train using flow-through cowcatcher. Journal of Central South University. https://doi.org/10.1007/s11771-025-6148-3
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Frequently Asked Questions
What is the main purpose of the flow-through cowcatcher?
The flow-through cowcatcher is designed to mitigate aerodynamic noise generated from the leading bogie region of high-speed trains by suppressing flow separation and promoting stable vortex evolution.
How was the effectiveness of the flow-through cowcatcher evaluated?
The effectiveness was evaluated using WALE-LES combined with FW-H acoustic analogy, and validated through semi-anechoic wind tunnel experiments.
What were the key quantitative results?
The flow-through cowcatcher reduced high-amplitude wall pressure fluctuations by up to 40%, decreased far-field sound pressure levels by 0.4–0.6 dB(A), and reduced the dominant sound source intensity by about 1.0 dB(A).
What is the significance of this study for high-speed train design?
The study provides theoretical insight and engineering guidance for structural optimization and low-noise design of the nose car in high-speed trains.
Which journal published this research?
The research was published in the Journal of Central South University, 2025, volume 32, issue 12, pages 4812-4826.
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