Aerodynamic Performance Of High-speed Train Research Articles

Effects of windbreak types on aerodynamics of high-speed trains traversing from flat ground to semi-cutting and semi-embankment under crosswinds

Under the operation of strong crosswinds, the aerodynamic performance of high-speed trains (HSTs) will be seriously deteriorated when the transition section of flat ground and semi-cutting and semi-embankment (FGSCSE) is traversed, and the setting of windbreaks will help to slow down the impact of strong crosswinds on the trains. In this study, a three-dimensional coupled computational fluid dynamics numerical model to assess the aerodynamic performance of train–windbreak–FGSCSE–air system is developed. A comparative assessment is carried out to identify the variations in aerodynamic performance on the train carriage: no windbreak (NW), 50% ventilation windbreak (VW), and solid windbreak (SW), and the reasons for these variations are elucidated by examining the flow field structure's evolution. Furthermore, the operational safety of the train is discussed based on the indicator of wheel unloading ratio (fΔQ). Across the three distinct conditions, significant abrupt changes in aerodynamic load coefficients (ALCs) and the shedding of vortex structures are experienced by HSTs traversing the FGSCSE transition sections. Compared to the VW condition, the NW and SW conditions result in a greater number of shedding vortices on the leeward side and the tail of the train, and the VW condition results in the smallest magnitude of ALCs fluctuation. The power spectral density peak values of the aerodynamic loads follow the order: SW > NW > VW. Upon the train fully enters the subsequent operational environment, the VW condition has the smallest standard deviation of these coefficients. The standard deviations of CFy, CFz, CMx, CMy, and CMz for the head train in the VW condition are only 57.17% (46.81%), 55.85% (54.15%), 72.74% (34.62%), 57.99% (51.92%), and 44.60% (43.82%) of the corresponding values in the NW (SW) condition, respectively. In the NW, VW, and SW conditions, the fΔQ exceeds 0.9 when the wind speeds reach 30, 40, and 35 m/s, respectively. The windbreak with a ventilation rate of 30% performs the best, providing the most effective safety and stability for train operation.

Evaluation of active leeward side air-blowing layout on the lateral aerodynamic performance of high-speed trains in crosswinds environment: Sustainable and safe operation strategy

The lateral aerodynamic forces experienced by high-speed trains operating in crosswind environments affect trains' operating safety significantly. This paper used the Improved Detached Eddy Simulation (IDDES) method based on the Shear Stress Transport (SST) k-ω turbulence model to explore the mitigating effect of air-blowing at the leeward side of the train on the train's lateral aerodynamic forces. Different air-blowing positions and speeds were considered. The results indicate that the best mitigating effect can be achieved when simultaneously blowing air at the head, middle, and tail cars; in addition, when blowing air at the speed of 0.3 times of the resultant velocity, the rolling moment of the three cars reduced by 7.71%, 7.25%, and 25.46% respectively. Finally, the assessment of the mitigation efficiency was displayed to discuss the trade-off of rolling moment reduction and energy utilization rate for air-blowing. The research gives an insight into increasing the stability and safety of trains in crosswind based on active control, which can improve the safe operation threshold of trains.

Influence of Anteroposterior Symmetrical Aero-Wings on the Aerodynamic Performance of High-Speed Train

Influence of Anteroposterior Symmetrical Aero-Wings on the Aerodynamic Performance of High-Speed Train

Impact of bogie fairing configuration on the aerodynamic performance of high-speed train under crosswind

In this paper, the unsteady aerodynamic characteristics of a three-car grouped high-speed train (HST) with different bogie fairing configurations under the crosswind are studied using improved delayed detached eddy simulation (IDDES) at Re = 1.85 × 106. The numerical method results are validated against the previous wind tunnel experiments. There are three cases with original half-fairing configuration (HFC), non-fairing configuration (NFC) and full-fairing configuration (FFC), respectively. The numerical results show that the bogie fairing configuration has significant effects. Compared to the HFC case, the drag force coefficients of the head, middle and tail cars with NFC increase by 53.13%, 14.87% and 27.04%, and corresponding parts of the FFC case decrease by 49.98%, 24.40% and 12.41%, respectively. The FFC case can also optimize the pressure distribution on the windward and leeward sides of the HST, and the flow structure and vertex distribution around the car body are also optimized. In addition, the increasing encirclement of the fairing configurations reduces the maximum lateral flow velocity inside the bogie cavities by 70% for HFC and 50% for FFC compared to the NFC. Overall, the FFC presents better aerodynamic performance than the NFC and HFC cases under crosswind, which is recommended for the design of the HST.

Numerical study on the effect of pantograph fairing on aerodynamic performance at various train heights

The pantograph is one of the primary sources of aerodynamic drag and noise during the operation of a high-speed train. To investigate the impact of the pantograph fairing on the aerodynamic performance at various train heights, six computational models are established, and the Improved Delayed Detached Eddy Simulation method is employed. The results indicate that the installation of the fairing can effectively reduce the aerodynamic drag coefficient of the high-speed train and pantograph at different train heights. As the train height increases, the drag reduction effect of the fairing enhances when the sinking platform coexists. The overall drag reduction rate of up to 4.30% can be achieved at a train height of 4000 mm. However, the larger reduction rate of 58.32% in the pantograph's drag coefficient at a train height of 3700 mm indicates that the fairing could make a greater effect on the pantograph at a smaller train height. The reduction in train height and pantograph sinking height leads to an increase in drag coefficient on the tail car, and the implementation of the fairing further amplifies the drag. This work offers a reference for optimizing the aerodynamic performance of high-speed train.

Wake dynamic characteristics of windproof structures in embankment–bridge sections along a high-speed railway under natural strong crosswinds

A recent trend in railway development around the world is the extension of high-speed railways to areas with harsh climatic environments. The aerodynamic performance of high-speed trains deteriorates when they run through embankment–bridge sections in a windy environment, posing potential safety risks. The present study aims to reveal the evolution mechanism of wake field in the transition section of the windbreak wall and wind barrier under natural strong crosswinds. First, the fluctuating characteristics of natural wind field collected by ultrasonic anemometers during a period of strong wind are captured. Next, the improved delayed detached eddy simulation scheme combined with the shear stress transfer k–w model is used to elucidate the difference of flow field modes on the leeward side of the windproof structure in the transition section under the conditions of constant and fluctuating crosswinds. Finally, the effects of model scale ratio (1:20, 1:10, and 1:1) on wind field simulation results on the leeward side of the windproof structure are revealed. Results show that the incoming flow with time-varying velocity evokes the instability of wake vortices of the windbreak wall in the embankment. The transient evolution results of the vortices obtained by the 1:10 model are in good agreement with those of the 1:1 model, whereas the results obtained by the 1:20 model have a large deviation.

Pedigree Aerodynamic Shape Design of High-Speed Trains

The aerodynamic performance of high-speed trains is closely related to their head shape. As each train set has its own modelling system, the aerodynamic shape design of head type of a high-speed train must follow a pedigree modelling approach. The train pedigree characteristics directly reflect its aerodynamic performance. The focus of this study is the extraction and application of the Shinkansen train pedigree features. First, large-scale differences in train head shapes are eliminated by dimensionless elimination. Second, the Shinkansen model pedigree features are extracted using similarity calculations. Finally, based on the constraint range of pedigree features on the new model shape, the concept head shape is designed with reference to the shape and surface parameters of high-speed trains, and its aerodynamic performance is verified. The results of the aerodynamic verification indicate that the concept design reduces the drag by more than 10% compared to the E2 Series base model. Additionally, the results demonstrate that the extraction and design application of train pedigree features can help a new train to develop its aerodynamic shape within its own pedigree modelling system, thus enabling the synergistic design of train shape and aerodynamic performance.

Research of aerodynamic performance of high-speed train crossing canyon with CFD simulation

Research of aerodynamic performance of high-speed train crossing canyon with CFD simulation

The effect of covering structure in pantograph sinking platform on the aerodynamics of high- speed train

ABSTRACT The aerodynamic drag of pantograph system hinders the increase of train operating speed, which can be reduced by the covering structure proposed in this study. Exploring the drag reduction mechanism of covering structure is critical. An IDDES method based on the SST κ–ω turbulence model was utilized to study the effect of covering structure on aerodynamic performance of high-speed train. The results show that the covering structure reduces the overall drag by 5.6% for 3-car train-set since the impingement of incoming flow on the surface of sinking platform is alleviated. The aerodynamic drag of the middle car is significantly reduced while that of the tail car increases due to higher pressure on the train joint surface caused by the covering plates. The turbulence of the flow field surrounding sinking platform is suppressed by weakening the flow separations from cavity edge. Vortical structure changes occur to the vortices shed from the leading edge of cavity because the front covering plate delays the process of flow separation, further leading to the alteration of dominant frequencies for folded pantograph. The covering structure will decrease the oscillation of lift force by 24.74% and 37.14% for lifted and folded pantograph.

A Study of Crosswind Characteristics on Aerodynamic Performance of High-Speed Trains on Embankment

A Study of Crosswind Characteristics on Aerodynamic Performance of High-Speed Trains on Embankment

The recent progress and state-of-art applications of aerodynamics for vehicle

Transportation is an indispensable part of human beings’ daily life, thus plenty of scholars have focused on improving the energy efficiency of transportation. The application and development of aerodynamics is of paramount importance. In this article, the effects of three types of locomotives on aerodynamic performance of high-speed trains are investigated. In order to lucubrate this topic, the definition of aerodynamics by different scientists is firstly discussed and showed, they basically classify them by three different kinds of ways. Subsequently, the creation of aerodynamics, historical development, and present situation are briefly introduced. In the main part, mathematical model and calculation formula are carried out to ensure which kinds of aerodynamic model is the most suitable among all the designs. Overall, these results offer a guideline for how to design a more effective and practical train head by applying the aerodynamic knowledge and expanding people's use of aerodynamics.

Effect of Vortex Generators on the Aerodynamic Performance of High-Speed Trains

Effect of Vortex Generators on the Aerodynamic Performance of High-Speed Trains

Comparison of aerodynamic performance of high-speed train driving on tunnel-bridge section under fluctuating winds based on three turbulence models

The coupled effect of canyon winds and rapid switching of operating scenes deteriorate the aerodynamic performance of the high-speed train (HST) running on the tunnel-bridge section (TBS). What's more, when investigating the aerodynamic performance of the HST by using CFD simulations, the calculation results obtained by various turbulence models show differences, which may have an uncertain effect on analysing the research results. This study aims to analyse the difference in calculation result of three turbulence models, when the HST running on the TBS. For this purpose, based on three mainstream turbulence models (LES, IDDES, and URANS) and the ‘mosaic’ meshing technology, a full-scale CFD dynamic model of 3D train–tunnel–bridge–air was established. Based on the on-site wind field sampling date, UDF program was compiled to load the aforementioned wind-speed time sequence on the velocity-inlet boundary, and the incoming wind field of the TBS was reconstructed. Finally, the aerodynamic load time history and flow field structure of the HST simulated by three turbulence models were revealed, when the HST was running on the TBS. The following conclusions were obtained. The time history of aerodynamic load changes and the fluctuation amplitude calculated by the two turbulence models of IDDES and LES are basically consistent (the difference is kept within 10%), when the HST running on the TBS. The influence of the turbulence model on the aerodynamic loads of the HST is mainly reflected in the head carriage, especially the side force. When the HST runs on the TBS, the side force, lift force, rolling moment, yawing moment and pitching moment of the head carriage calculated by the URANS model are 16%, 9%, 29%, 20%, and 13% higher than the corresponding values of the LES model. Based on the equivalent principle of the side force of the head carriage, a formula is proposed to quantitatively describe the relationship between the side force amplitude of the head carriage on the TBS calculated by the URANS model and the corresponding value of the LES model. The formula can be used to correct the boundary inflow wind speed conditions of the URANS model, so as to quickly obtain the calculation results equivalent to the LES model.

Effect of simplifying bogie regions on aerodynamic performance of high-speed train

Effect of simplifying bogie regions on aerodynamic performance of high-speed train

Multi-objective aerodynamic optimization of high-speed train heads based on the PDE parametric modeling

With the increasing running speed, the aerodynamic issues of high-speed trains are being raised and impact the running stability and energy efficiency. The optimization design of the head shape is significantly important in improving the aerodynamic performance of high-speed trains. Existing aerodynamic optimization methods are limited by the parametric modeling methods of train heads which are unable to accurately and completely parameterize both global shapes and local details. Due to this reason, they cannot optimize both global and local shapes of train heads. In order to tackle this problem, we propose a novel multi-objective aerodynamic optimization method of high-speed train heads based on the partial differential equation (PDE) parametric modeling. With this method, the half of a train head is parameterized with 17 PDE surface patches which describe global shapes and local details and keep the surface smooth. We take the aerodynamic drag and lift as optimization objectives; divide the optimization design process into two stages: global optimization and local optimization; and develop global and local optimization methods, respectively. In the first stage, the non-dominated sorting genetic algorithm (NSGA-II) is adopted to obtain the framework of the train head with an optimized global shape. In the second stage, Latin hypercube sampling (LHS) is applied in the local shape optimization of the PDE surface patches determined by the optimized framework to improve local details. The effectiveness of our proposed method is demonstrated by better aerodynamic performance achieved from the optimization solutions in global and local optimization stages in comparison with the original high-speed train head.

Wind tunnel measurement of aerodynamic characteristics of trains passing each other on a simply supported box girder bridge

The aerodynamic performance of high-speed trains passing each other was investigated on a simply supported box girder bridge, with a span of 32 m, under crosswinds. The bridge and train models, modeled at a geometric scale ratio of 1:30, were used to test the aerodynamic forces of the train, with the help of a designed moving test rig in the XNJD-3 wind tunnel. The effects of wind speed, train speed, and yaw angle on the aerodynamic coefficients of the train were analyzed. The static and moving model tests were compared to demonstrate how the movement of the train influences its aerodynamic characteristics. The results show that the sheltering effect introduced by trains passing each other can cause a sudden change in force on the leeward train, which is further influenced by the wind and running speeds. Detailed analyses related to the effect of wind and train speeds on the aerodynamic coefficients were conducted. The relationship between the change in aerodynamic coefficients and yaw angle was finally described by a series of proposed fitting formulas.

Influence of wind barrier on the transient aerodynamic performance of high-speed trains under crosswinds at tunnel–bridge sections

Porous wind barriers (PWBs) are gradually applied to tunnel–bridge–tunnel infrastructures (TBTIs) along high-speed railway lines. Due to the remarkable aerodynamic effect of high-speed trains (HSTs), the windproof performance of a PWB at tunnel–bridge section (TBS) is particularly critical when a HST passes through the TBTI under crosswind. And it seems to be easily ignored by researchers. This study aims to determine the influence mechanism of the PWB in the TBS. A CFD dynamic model of air–train–PWB was built based on porous media theory, and its reliability is verified by model and field tests. The main results are as follows: the corresponding variation amplitudes of the train’s aerodynamic load coefficients are reduced by 36–95% when a PWB is set in the TBS; adopting the same design parameters along the full-length PWB on the TBTI is unreasonable; the PWB height and porosity in the TBS must be increased and reduced more than 33%, respectively, to achieve equivalent windproof performance. The conclusions in this paper can provide a preliminary idea for the optimization design of the PWB on the TBTI.

Comparison of Aerodynamic Characteristics of High-Speed Train for Different Configurations of Aerodynamic Braking Plates Installed in Inter-Car Gap Region

An improved delayed detached eddy simulation based on a shear–stress transport κ–ω turbulence model is used to investigate the aerodynamic characteristics of a high-speed train with an aerodynamic braking plate installed in the inter-car gap (ICG) region. The flow field and the aerodynamic performance of high-speed trains with different aerodynamic braking plate configurations are compared and analysed. The numerical method used in this study is verified through a wind tunnel test. Results show that opening the plates installed in the ICG significantly increased the aerodynamic drag of the train, especially large downstream plates with relatively small fluctuations in the aerodynamic forces relative to those of large upstream plates. The braking plates significantly affected the levels of downstream ICG turbulence, which then interacted with the external flow to reduce the wake profile.

Transient aerodynamic performance of high-speed trains when passing through an infrastructure consisting of tunnel–bridge–tunnel under crosswind

The running safety risk of a high-speed train (HST) deteriorates remarkably under crosswind when the train drives into a bridge from a tunnel (OUT) or from a bridge into a tunnel (IN). This study aims to reveal the difference in the aerodynamic performance of HSTs in the two processes in terms of transient aerodynamic loads and flow field. A calculation approach for aerodynamic loads in which the carriage surface is divided into segments in longitudinal and circumferential directions is proposed to obtain the real-life time history of aerodynamic loads. The main results can provide a theoretical basis for traffic safety command when HSTs run in an infrastructure scenario consisting of tunnel–bridge–tunnel (ISTBT). In the presence of crosswinds, the maximum fluctuation amplitudes of five aerodynamic coefficients in the processes ‘OUT’ and ‘IN’ are increased by 2.1–83.8 and 4.0–84.3 times, respectively. The fluctuation amplitudes of five aerodynamic coefficients in the process ‘IN’ are generally 1.01–2.32 times larger than those in the process ‘OUT’ in a crosswind environment. A large resultant wind angle causes the fluctuation amplitudes in the five aerodynamic coefficients in the process ‘IN’ to be larger than those in the process ‘OUT’. The maximum fluctuation amplitude of aerodynamic coefficients in leading and tail carriages is the key to controlling traffic safety when HSTs run in ISTBT in a crosswind environment.

Transient aerodynamic performance of high-speed trains when passing through two windproof facilities under crosswinds: A comparative study

Windbreak (WB) and anti-wind open-cut tunnel (AOT) are two common windproof facilities for high-speed railways in windy areas. This study aims to determine which of them has better aerodynamic performance. For this purpose, the transient aerodynamic loads of high-speed trains are compared when passing through two windproof facilities under the same conditions of train and crosswind speeds via CFD simulation. The sudden change mechanism of aerodynamic loads and the differences in aerodynamic loads between the AOT and WB cases are revealed from the perspectives of flow field and pressure. Four main conclusions are obtained. Firstly, the fluctuation amplitudes of the five aerodynamic loads of each carriage in two periods (entry and exit) are remarkably greater than those in other periods (completely running in crosswind or windproof facilities). Secondly, the maximum fluctuation amplitudes of the five aerodynamic loads of the head carriage are generally greater than those of the rear and middle carriages during the period of entry (or exit). Thirdly, the maximum fluctuation amplitudes of side force, lift force, rolling moment, yawing moment and pitching moment of the head carriage in the WB case are 1.42, 0.84, 1.42, 1.45 and 1.44 times for the period of entry and 1.2, 1.24, 1.2, 1.58 and 2 times for the period of exit, respectively, compared with those in the AOT case. Fourthly, the maximum change rates at a time interval of 0.035 s of the side force, lift force, rolling moment, yawing moment and pitching moment of the head carriage in the WB case are 1.32, 1.26, 1.32, 1.57 and 1.52 times for the period of entry and 1.13, 1.24, 1.13, 1.42 and 1.69 times for the period of exit, respectively, compared with those in the AOT case.