Structural coupling vibrations induced by large-mass underframe equipment in high-speed trains have become increasingly prominent, particularly due to the unresolved first-order vertical bending characteristics. The use of conventional rubber isolators often leads to in-phase and anti-phase vibration modes near 10 Hz. To address this issue, a nonlinear broadband damping strategy based on particle dampers is proposed. The damping ratio of the particle damper is first determined using the Discrete Element Method (DEM), and subsequently integrated into a coupled dynamic model of the car body and underframe equipment for model correction. A finite element (FE) model is then developed and validated through scaled experimental testing to systematically evaluate the influence of particle dampers on low-frequency vertical bending behavior. Results demonstrate that iron-based alloy particle dampers (90% filling ratio, 3 mm diameter) significantly broaden the resonance bandwidth, reduce dual-peak amplitudes by 33.51% and 26.02%, and markedly enhance the overall stability of the system.

The air compressors in a locomotive's air supply system are located in confined spaces within the locomotive. Operating continuously under high loads and high temperatures, they generate significant heat and face challenges in heat dissipation. Therefore, this paper uses numerical simulation methods to analyze the effects of the air inlet louver porosity and exhaust configuration on the heat dissipation performance of an air conditioning (AC) unit under extreme ambient temperatures (55 degrees C), and verifies the reliability of the results through algorithmic validation. The results indicate that the temperature distribution on the surface of the AC unit is highly uneven and closely correlated with the local flow velocity distribution. Although there is a linear relationship between the inlet aperture area and the surface temperature of the AC unit, the heat dissipation benefits achieved by adjusting the aperture area alone are not significant. Further analysis revealed that while closing the top cover enhances convective heat transfer, it also leads to an increase in the air flow temperature. In response, this study proposes an integrated optimization scheme that combines a closed top cover with side-wall exhaust ventilation. This scheme enhances surface convective heat transfer while simultaneously lowering the air flow temperature, resulting in a 12.6% and 10.0% decrease in the average surface temperatures of AC1 and AC2, respectively, and significantly reducing the ambient temperature in the machine room. The research findings reveal the mechanisms by which ventilation parameters affect heat dissipation performance, providing valuable guidance for the thermal design of locomotive auxiliary systems.

Previous studies have demonstrated that the Ensemble Kalman Filter (EnKF) has been successfully applied to optimize turbulence model constants under various flow conditions, particularly in two-dimensional cases. However, in engineering applications, the flow fields are often three-dimensional and highly nonlinear. Under such conditions, due to the non-uniqueness of the optimal solution in the inverse problem, directly applying the conventional EnKF often yields unsatisfactory results. To address this challenge, this study combines proper orthogonal decomposition (POD) with EnKF to develop a POD-reduced EnKF algorithm for data assimilation in complex three-dimensional flow fields of high-speed trains. By extracting flow field characteristics through POD, the number of observation points is reduced, which significantly enhances the data assimilation accuracy. Results show that the assimilated turbulence model constants lead to good agreement between simulation and experimental data for a high-speed train operating in open-air conditions. The method also demonstrates strong robustness, achieving consistent assimilation performance across different numbers and locations of observation points. In addition, the optimized constants exhibit a certain degree of generalizability, improving prediction accuracy across different inflow conditions and geometries. The proposed framework offers a promising strategy for enhancing aerodynamic modeling of high-speed trains.

Rolling bearings undergo progressive degradation during service, where localized raceway defects evolve from initial pitting to extended wear, often exhibiting asymmetric defect-edge geometries and shoulder formation. Such geometric evolution plays a critical role in failure development but is inadequately represented in conventional dynamic models based on rectangular or idealized defect assumptions, limiting their ability to explain failure-induced vibration responses observed in practice. This study develops a physics-based dynamic model to investigate the failure mechanisms associated with asymmetric edge-wear evolution of raceway defects. The model explicitly incorporates evolving edge profiles and shoulder geometries through piecewise displacement excitation functions, enabling a mechanistic description of rolling-element motion and transient contact interactions across different defect regions. A direct relationship is thereby established between defect morphology, transient contact forces, and vibration responses. The proposed model is validated using finite element simulations of contact forces and experimental vibration measurements under defective conditions. Results show that neglecting defect-edge evolution leads to systematic overestimation of impact severity in rectangular defect models, whereas edge steepness and shoulder height dominate transient impact intensity and vibration persistence. These findings explain why defects of identical length can produce markedly different vibration amplitudes. By clarifying the role of defect geometry in failure-related dynamics, this work provides a mechanism-oriented interpretation of bearing vibration behavior and offers quantitative parameters for vibration-based fault diagnosis, defect localization, and prognosis, contributing to improved bearing health monitoring and reliability assessment.

Next-generation high-speed trains operating at 450 km/h face critical pantograph stability challenges. Intense roof-level airflow degrades aerodynamic performance and induces aeroelastic vibrations, compromising contact stability, accelerating fatigue, and threatening structural integrity. To address these issues, a bidirectional FSI computational model is developed using ANSYS Workbench. Fluent and Mechanical are employed to solve the fluid and structural fields, respectively, with System Coupling enabling node-level data exchange. The fluid field is modeled using the RANS equations with the SST k-omega turbulence model, while a flexible pantograph model is adopted for the structural field. The "moving catenary, stationary pantograph" concept and the Augmented Lagrange contact algorithm are applied to simulate aeroelastic behavior at 450 km/h. The results indicate that FSI coupling increases the pantograph lift by more than 8% compared to uncoupled simulations, while significantly attenuating aerodynamic load fluctuations. Furthermore, the aerodynamic excitation is found to facilitate the redistribution of vibration energy within the pantograph system. The mean and standard deviation of the contact force are 320 N and 119 N, respectively. Maximum stress reaches 116 MPa at the arc transition of the pantograph head suspension rib, yielding a safety factor of 1.07 and indicating the need for structural reinforcement.

During the trial operation of a certain electric multiple unit,it was found that although the noise amplitude in the passenger compartment above the traction motor met the limit standard requirements when operating at speeds between 100 and 160 km/h.However,during the traction and braking processes,there were distinct frequency peaks in the traction motor noise,affecting passenger comfort.To improve the ride comfort during this speed range,without affecting the performance of the traction system,rectifications were made to address the motor noise issue.Measures such as adjusting the switching frequency and modifying the direct current voltage were proposed to optimize the traction control software.Through comparative testing of different control measures,the most effective control measure was selected,which effectively eliminated the single-frequency noise of the motor in this speed range.Additionally,a safety assessment was conducted to demon-strate that the new motor traction measures met the requirements for traction and operational reliability.

The construction of the railway network is advancing steadily, with a substantial increase in the number of railway tunnels. Among these tunnels, the proportion of double-track tunnels has risen significantly. Along with this trend, the pressure wave superposition effect caused by train crossings in double-track tunnels has become a critical issue, posing threats to the structural integrity of tunnels and passenger comfort. To address this issue, a double-track train wave signature (TWS) model is proposed, based on the principle of characteristic wave superposition. The first part of the paper introduces the principle of the single-track TWS method, outlines the construction of the double-track TWS method, and briefly describes the three-dimensional (3D) numerical model used. The proposed double-track TWS method is then validated through both field measurements and 3D numerical simulations. This is followed by an analysis of the propagation and evolution of wave systems within the tunnel during train crossings. Finally, the paper presents a systematic investigation of tunnel wall pressure amplitude variations resulting from different train entry timings. Key findings indicate that the TWS method achieves sufficient accuracy in simulating tunnel wall pressure for both single- and double-track configurations, with peak-to-peak errors within 10%, except at points near tunnel portals. For double-track crossings at constant speed, the maximum and minimum pressures, as well as peak-to-peak values on tunnel walls, exhibit periodic-like fluctuations with crossing positions. This phenomenon becomes more prominent in shorter tunnels. Moreover, adjusting the entry time difference between trains may even reduce peak-to-peak pressure values on tunnel walls by 50%, offering a theoretical foundation for optimizing train scheduling and tunnel design.

Urban railways alleviate traffic congestion and enhance transportation efficiency. The operation of trains in tunnels can cause significant pressure waves, resulting in passenger discomfort and auditory damage. Therefore, airtight train configurations were employed to mitigate interior pressure fluctuation. To ensure interior air quality, controlled ventilation through air-conditioning units (ACUs) is required. However, during tunnel operations, pressure waves enter the carriage through ACUs, thereby affecting the interior pressure. Considering that the on-off plates of air intakes may malfunction, the influence of tunnel pressure waves on the auditory comfort of passengers is worth investigating. In this study, a full-scale test was conducted to investigate the spatiotemporal distribution characteristics of the interior/exterior pressure variation induced by trains with different lengths passing through tunnels at multiple speeds. The ACU air intake operates in three states: automatic control (closed), 1/4 open, and fully open. An inverse correlation was observed between train length and interior/exterior pressure variation. Compared with the driver's cab, the interior pressure of the passenger compartments was more affected by the train length (with a difference of approximately 30%). The operational state of ACU air intakes significantly impacts interior pressure variations, with closed intakes effectively reducing fluctuations, whereas opening size demonstrated limited influence. Both the amplitude and variation of the interior/exterior pressure exhibited positive correlations with train speed. These findings inform optimized ACU intake control strategies for enhancing passenger auditory comfort.

The bogie compartment area of high-speed trains has been identified as a major source of aerodynamic noise during high-speed operation. To effectively reduce aerodynamic noise at this area, a noise reduction method based on serrated leading-edge vortex generators is proposed. Large eddy simulation (LES) and the Ffowcs Williams-Hawkings (FW-H) acoustic equation were used to numerically simulate aerodynamic noise at the bogie area based on a 1:8-scale simplified bogie model at a train speed of 400 km/h. The analysis examined the effects of serrated vortex generator heights of 20 mm, 40 mm, and 60 mm on the flow field disturbance, vortex shedding, and sound radiation characteristics at the bogie area. Numerical simulation results indicated that the serrated structures with a height of 40 mm were most effective in noise reduction within the 500 Hz frequency band, reducing wall-mounted dipole acoustic energy by up to 36%; the 40 mm high serrated vortex generators reduced far-field radiated noise by an average of 0.5 dB, with the maximum noise reduction reaching 2 dB. These effects are mainly due to the optimization and regulation from the vortex generators' characteristics to separate the shear flow at the front edge of the bogie area and to disturb spanwise vortices, which effectively weaken low-frequency noise caused by vortex shedding and shear layer instability, and suppress the self-sustained oscillation of Rossiter modes. The study shows that serrated leading-edge vortex generators significantly improve aerodynamic noise distribution at the bogie area, with the greatest noise reduction observed for the 40 mm height. These findings offer an effective approach to aerodynamic noise control at the bogie area.

The bogie area with a complex structure is an extremely important source of noise for trains. Based on the large-eddy simulation(LES) and Ffowcs Williams-Hawkings(FW-H) analogy, aero-acoustic simulation was conducted on a 3-car high-speed train of a certain type with a bogie cavity bottom plate installed on the front and rear cars. The results show that bottom plate changes the flow field around the bogie, weakens the flow separation of airflow at the leading edge of the bogie cavity, mitigates the flow impact of airflow on various components of the bogie, suppresses the formation and detachment of large-scale vortices in the bogie area, and reduces the formation of pressure pulsations on the geometric surface of the bogie area. The bogie cavity bottom plate scheme reduces the far-field aerodynamic noise of the train by 1.63dBA, and the noise reduction effect is significant. The aerodynamic noise of the measurement point equipped with a bogie cavity bottom plate is lower than that of the conventional bogie cavity in all frequency bands, and the energy reduction is more significant at medium and low frequencies.

A simulation framework for three-dimensional particle trajectory tracking, snow accumulation and ice accretion modelling on solid bodies in high-speed air flow is presented. The framework, named HADICE, solves the aerodynamic flow field as Reynolds averaged Navier-Stokes (RANS), with optional hybrid RANS/LES capabilities for modelling complex turbulent flows. Particle trajectory tracking is performed in an Eulerian-Lagrangian approach and wall collision is modelled using a hard collision model with reflect condition and a momentum based trap condition. A novel accurate and robust iterative evaluation method for the local collection efficiency is proposed for arbitrary 3D geometry and flow. Ice accretion is modelled in a multi-step approach and iced geometry is updated through mesh deformation using a radial basis function (RBF) interpolation method. Snow accumulation and ice accretion predictions based on the framework are validated against climatic wind tunnel experimental measurements. A full 3D simulation is demonstrated for snow accumulation and ice accretion on a 1:8 scaled high-speed train model. Using the presented framework, snow accumulation and icing simulation for high-speed trains can be conducted in an accurate and efficient manner, which is of great importance for physical investigations and the design of anti-snow and ice protection systems.

This paper discusses the contribution of the quadrupole noise source on the aerodynamic noise of the high-speed maglev train. The computational method of the aerodynamic noise considering the quadrupole noise source is presented, and the aerodynamic noise characteristics of the high-speed maglev is studied. The study shows that the dipole noise sources of the high-speed maglev train are mainly distributed on the bottom of the head car, the bottom and body of the tail car, the bottom and inside of the suspension frame. The contribution of the quadrupole noise source is more reflected in the low-frequency range. The aerodynamic noise energy of the high-speed maglev train caused by the quadrupole noise source accounts for 42% at the train speed of 600km/h.

High-entropy alloy (HEA) coatings have demonstrated great potential in anti-wear applications. To further improve the mechanical and tribo-corrosion properties of the HEA coatings, the VAlTiMoSi, (VAlTiMoSi)80C20, and (VAlTiMoSi)60C40 coatings were successfully deposited by DC magnetron sputtering. The microstructure, mechanical, and tribo-corrosion properties of as-deposited and heat-treated coatings were analyzed. All the as-deposited HEA coatings were BCC + amorphous phases. The thermal effect promoted the formation of intermetallic compounds, and the C inhibited the formation of Mo3Si and Ti5Si4. The hardness and elastic modulus of the heat-treated VAlTiMoSi coating were 20.1 and 294.0 GPa, respectively. The heat-treated (VAlTiMoSi)60C40 coating showed the lowest wear rate, namely 5.2 × 10−14 m3·Nm−1, and the best formation ability of passive film in 3.5 wt% NaCl solution.

Synchronous analysis is one of the most effective and practical techniques in rotating machinery diagnostics, especially in cases with variable speed operations. A modern analog-to-digital convertor (ADC) usually digitizes an analog signal to an equal time interval data series. Synchronous resampling converts the data series from an equal time interval data series to an equal shaft rotation angle interval data series. This conversion is usually achieved in the digital domain with the aid of shaft speed information, through either direct measurement or identification from a measured vibration signal, which is a time-consuming process. In order to improve the computational efficiency as well as the data processing accuracy, in this paper, a fast synchronous time-point calculation method based on an inverse function interpolation procedure is proposed. By identifying the inverse function of the instantaneous phase with respect to time, the calculation process of synchronous time points is optimized, which results in improved calculation efficiency and accuracy. These advantages are demonstrated by numerical simulations as well as experimental verifications. The numerical simulation results show that the proposed method can improve calculation speed by about five times. The synchronous analysis based on the proposed method was applied to a bearing fault detection in a high-speed rail carriage, which demonstrated the advantages of the proposed algorithm in improving the signal-to-noise ratio (SNR) for bearing damage feature extraction.

This research explores the ability of multiple small air chambers, distributed along railway tunnels, to suppress wavefront steepening and aims to find an effective method to prevent the radiation of unacceptable pressure disturbances from tunnel portals. It does so by utilizing the existing idle space in the tunnel, such as under walkways, and investigates the influence of moderately underdamped air chambers on wavefront evolution. This complements previous work, in which the chambers are assumed to be overdamped. In the early part of the paper, the validity of the numerical method used in this paper is verified through various means, including experiments with specially constructed air chamber model. Next, differences in the indicative influence of the wavefront, between underdamped and overdamped chambers, are compared. The asymptotic state of the wavefronts, in tunnels equipped with underdamped chambers, is then considered, along with a corresponding sensitivity study, centred on a specific base case. After that, the reasons for the large wavefront gradient caused by the underdamped chamber are discussed. Finally, the effect of installing a check valve at the chamber connection on wavefront evolution is explored. It is found that a moderately underdamped chamber may have a greater potential to suppress wavefront steepening to that of an overdamped chamber, especially for wavefronts with amplitudes up to 4 kPa. However, the presence of significant inertia at the chamber connection could result in the wavefront continuing to steepen for a distance of 2-3 km. Therefore, it is advisable to exercise more caution when employing underdamped chambers in shorter tunnels. While the check valve may have a certain degree of mitigating effect on wavefront steepening, but its impact is not significant.

Contagious pathogens like COVID-19 transmitted via respiratory droplets spread effortlessly in the passenger compartments of transport, significantly jeopardizing passengers’ safety when taking public transportation. To date, studies on the fundamental theories of airborne droplet transmission and the engineering application of decontamination techniques are insufficient for the prevention and control of pathogens transmitting in the compartments of passenger transport. It is essential to systematically investigate the control approaches to restrain pathogens from transmitting in passenger compartments. Herein, a theoretical framework for calculating the transmission of pathogens in a complex compartment environment was proposed, and experimental platforms that satisfy the Biosafety Level-2 Laboratory safety level for compartment environment simulations were built based on a set of real train cabins. On these bases, numerical investigations on the motion of pathogen-laden droplets were conducted, and decontamination techniques were examined experimentally. Thereby, control measures on the pathogen transmission and pathogen decontamination schemes were proposed. Moreover, highly efficient decontamination devices were developed, and coping strategies for epidemic emergencies were devised. The outcomes provide theoretical and technical support for developing the next generation of transportation and the prevention and control measures cooperatively considering regular and pandemic times.

Environmental problems caused by micro-pressure waves (MPWs) are increasingly prominent with increase in train speed. Considering different models of trains, which may have differences in nose lengths (Ln), and certain extreme terrains where it is unsuitable to construct the buffer hood outside the tunnel, this study numerically investigated the adaptive relationship between Ln and variable-section tunnel parameters [i.e., the length (L1) and area (S1) of the entrance expansion section] for minimizing the MPW. The results show that, as Ln rises from 5 to 13 m, the formation of the MPW peak is continuously delayed, and the peak value of the MPW decreases; while the optimal L1 remains at 20 m for different Ln. Additionally, the optimal S1 scarcely changes with the increase in Ln as well, between 151 and 156 m2, and its ratio to the section area of the main tunnel (70 m2) is approximately 2.2. The optimal parameters of the entrance expansion section play a universal role for trains with different Ln, which can alleviate the MPW amplitude with a value of 58% or higher. The findings can provide significant support for designing tunnels and tunnel hoods, focusing on alleviating acoustic noise.

为研究压缩波沿隧道传播演化的影响规律,采用考虑压缩波惯性效应和壁面摩擦效应的一维特征线法,建立了压缩波沿隧道传播演化的数值模型,通过一维平面波方程与实车测试两种方法共同验证了该模型的准确性.针对波前形状、车身波等、压力幅值关键因素,研究了初始压缩波沿隧道传播时,最大压力梯度的变化规律.在此基础上,进一步探讨分析了摩擦与气室阵列共同作用对压缩波波前演化的影响以及壁面摩擦的作用机理.结果表明:初始压缩波波形相同时,压缩波最大压力梯度随波前幅值的增大而增大;不同波形的初始压缩波沿隧道的演化规律不完全相同,但列车车身进入隧道所产生的车身波并不会影响压缩波波前的最大压力梯度;考虑壁面摩擦后,气室阵列对压缩波最大压力梯度的缓解效果有了进一步提高,壁面摩擦越大,缓解效果越显著.

In this paper, the flow characteristics of an air chamber inside a tunnel when subjected to train-nose-entry wavefronts were analyzed using numerical simulation. The results demonstrate that there exists a specific range of connection sizes for a fixed volume of air chamber, which imparts an under-damped characteristic to the chamber. Additionally, the pressure distribution within the air chamber and tunnel exhibits a noticeable three-dimensional effect as a consequence of the non-uniform flow field at the connection of the air chamber. The difference in the numerical results of the maximum pressure gradient is primarily observed at the air chamber connection when comparing the axisymmetric model to the one-dimensional model. However, this difference gradually diminishes to approximately 1% after the wavefronts have traversed through the air chamber for a distance of approximately 5 m. Furthermore, a scaled experimental setup was constructed to compare the obtained numerical results with the experimental data, successfully validating the accuracy of the numerical method.

The high-speed train's windshield structure is made of high strength rubber. The stagnation pressure under crosswind condition will lead to a large average deformation along with moderate flow-induced vibration of the windshield structure. This deformation and vibration have a vital influence on the servicing life and failure model windshield structures. In this study, the flow-induced deformation and vibration of windshields under crosswind condition are systematically analyzed through an experimentally verified numerical approach. The flow field and aerodynamic load around windshield structure, as well as the deformation of windshield structure are systematically investigated. The results indicate that, compared to the flat ground windless condition, the windshield's maximum deformation location under crosswind has shifted from the upper half to the lower half. Besides, among all windshield structures throughout the three car formation train, the downstream half of windward windshield between head car and middle car exhibits the largest deformation. When the wind angle shifts from 20° to 30°, the primary frequency of this maximum displacement location is around 30 Hz. In contrast, the primary frequency on the maximum displacement location of windward windshields between middle car and trailing car is 17.5 Hz.