High-speed Train Nose Research Articles

Investigation of transient aerodynamic pressure of a high-speed train nose passing from a stationary one in a high-speed rotary scaled test setup

ABSTRACT Measuring of high-speed train aerodynamic pressure is important in order to calculate the safety of train and track. There are many tests done in this area include full-scale tests to smaller scaled test setups in straight path. Usually setting up this aerodynamic testing equipment for high-speed trains requires very high cost and large space. In addition, they cannot set the exact amount of train speed in each point of path due to the rubber band motivating mechanism. So, in this study, a high-speed rotary scaled model (HRSM) test setup is introduced and constructed for measuring the transient aerodynamic pressure peak of high-speed train with the speed of up to 200 km/h. This test equipment can perform most aerodynamic tests of high-speed trains on a scale of 1–25; the needed area of the HRSM is about 30 times lower than conventional straight test rigs. This test setup is built not only reducing construction costs, but also has the ability to control accurate train speed in each point of path up to 200 km/h, compared with straight test setup. The accommodation of induced wind profiles in straight and rotary model is done in a short numerical simulation and a validation is done with other experimental results, which shows acceptable agreement in estimation of induced peak pressure in straight and rotary model. The results of this research provide valuable outcome as a fundamental for future studies.

A stacking-based ensemble prediction method for multiobjective aerodynamic optimization of high-speed train nose shape

A stacking-based ensemble prediction method is proposed in order to improve the efficiency and accuracy of aerodynamic shape optimization. This can be divided into a two-level model. The first-level model uses various base learners to predict the training dataset and obtain various combinations of predictions. In the second-level model, the meta-learner is trained using various combinations of predictions as inputs and the true response values as outputs. The RMSE and R-Square metrics results show that the performance metrics of the stacked models are significantly better than those of the original surrogate models, except for the stacked RBFNN model. The stacked Kriging model and LSSVR model achieved the best results with RMSE and R-Square index values of 0.0039 and 0.8418 for aerodynamic drag coefficient, respectively. The stacked Kriging model, RBFNN model, and LSSVR model achieved the best results with RMSE and R-Square index values of 0.0024 and 0.76 for aerodynamic lift coefficient, respectively. Four state-of-the-art multiobjective optimization algorithms are used to perform the optimization process. The results of hypervolume and Pareto fronts demonstrate the effectiveness of the selected FDV-NSGAII algorithm. After optimization, the drag and lift coefficients before and after optimization are reduced by 1.9% and 12.7%, respectively.

Effect of bogie fairing on aerodynamic and aeroacoustic behaviour of a high-speed train nose car

ABSTRACT The influence of bogie fairing on the flow feature and aerodynamic noise performance of a high-speed train nose car model is studied based on large-eddy simulation combined with acoustic analogy approach. For the case having no fairing, the strong flow interactions and impingements occur around the bogie cavity region due to the mass addition and expulsion induced from the cavity leading edges. When a streamlined fairing is mounted outside the bogie cavity, the fluid entrainment and vortices evolvement within the bogie cavity are weakened and the shear layer impingement and flow separation outside the fairing are mitigated greatly. Thus the wall pressure fluctuations on the solid surfaces of geometries located within bogie cavity are decreased and the flow-induced noise is reduced noticeably. Based on the semi-anechoic wind tunnel measurements on a high-speed train nose car model without and with bogie fairing, it is found that the dominant sound source around bogie cavity moves from its central area to rear wall region and the aerodynamic noise is reduced effectively with a streamlined fairing mounted around the bogie cavity. The numerical predictions of aerodynamic noise are verified by the experimental measurements. The investigation would be beneficial for guiding the low-noise design and configuration optimization of a high-speed train bogie fairing.

Research Progress of Aerodynamic Multi-Objective Optimization on High-Speed Train Nose Shape

Research Progress of Aerodynamic Multi-Objective Optimization on High-Speed Train Nose Shape

Multi-objective aerodynamic optimization design of high-speed maglev train nose

PurposeThe nose length is the key design parameter affecting the aerodynamic performance of high-speed maglev train, and the horizontal profile has a significant impact on the aerodynamic lift of the leading and trailing cars Hence, the study analyzes aerodynamic parameters with multi-objective optimization design.Design/methodology/approachThe nose of normal temperature and normal conduction high-speed maglev train is divided into streamlined part and equipment cabin according to its geometric characteristics. Then the modified vehicle modeling function (VMF) parameterization method and surface discretization method are adopted for the parametric design of the nose. For the 12 key design parameters extracted, combined with computational fluid dynamics (CFD), support vector machine (SVR) model and multi-objective particle swarm optimization (MPSO) algorithm, the multi-objective aerodynamic optimization design of high-speed maglev train nose and the sensitivity analysis of design parameters are carried out with aerodynamic drag coefficient of the whole vehicle and the aerodynamic lift coefficient of the trailing car as the optimization objectives and the aerodynamic lift coefficient of the leading car as the constraint. The engineering improvement and wind tunnel test verification of the optimized shape are done.FindingsResults show that the parametric design method can use less design parameters to describe the nose shape of high-speed maglev train. The prediction accuracy of the SVR model with the reduced amount of calculation and improved optimization efficiency meets the design requirements.Originality/valueCompared with the original shape, the aerodynamic drag coefficient of the whole vehicle is reduced by 19.2%, and the aerodynamic lift coefficients of the leading and trailing cars are reduced by 24.8 and 51.3%, respectively, after adopting the optimized shape modified according to engineering design requirements.

Improved Delayed Detached Eddy Simulation of the Slipstream and Trackside Pressure of Trains with Different Horizontal Profiles

The slipstream caused by high-speed trains may harm pedestrians and workers trackside. In general, the characteristics of the slipstream are influenced mainly by the nose shape of the train. The present study explores the slipstream caused by high-speed trains with three different horizontal nose profiles based on the results of three-dimensional, improved delayed detached eddy simulation (IDDES) with an unsteady turbulence model and a set of 1/8th scaled train models. The results obtained using this numerical methodology are in good agreement with those obtained from corresponding wind tunnel tests. The trackside pressure changes around the train models are also captured and analyzed. The analysis reveals that the width of the nose can significantly influence the magnitude and arrival time of slipstream velocity and pressure peaks. The results and proposed numerical methodology can be used as guidelines for the design of high-speed train nose shapes.

Aerodynamic Drag Reduction of a High-Speed Train Nose With Bionic Round Pits

The aerodynamic drag forces of a high-speed train with or without round pits were investigated. The aerodynamic drag reduction is mainly due to the pressure difference. The round pits installed on the coupling cover contribute nearly 2% for the aerodynamic drag reduction of high-speed trains.

Aerodynamic Study of Two Opposing Moving Trains in a Tunnel Based on Different Nose Contours

It is well known that the train nose shape has significant influence on the aerodynamic characteristics. This study explores the influence of four kinds of nose shapes (fusiform, flat-broad, bulge-broad, ellipsoidal) on the aerodynamic performance of two opposing high-speed trains passing by each other through a tunnel at 250 km/h. The method of three dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes equations and RNG k-ε double equation turbulence model was carried out to simulate the whole process of two trains passing by each other inside a tunnel. Then the pressure variations on tunnel wall and train surface are compared with previous full-scale test to validate the numerical method adopted in this paper. The assessment characteristics, such as transient pressure and aerodynamic loading, are analyzed to investigate the influence of nose shape on these assessment parameters. It is revealed that aerodynamic performance of trains which have longitudinal nose profile line B (fusiform, flat-broad shape) is relatively better when passing by each other in a tunnel. The results can be used as a guideline for high-speed train nose shape design.

Aerodynamic Effects of Inclined Portals on the Initial Compression Wave Generated by a High-Speed Train Entering a Tunnel

The micropressure wave radiated from a tunnel exit is one of the environmental problems which can be investigated from the temporal pressure gradient of the compression wave. The effects of inclined portals on the initial compression wave, specifically the maximum temporal pressure gradient, are numerically studied by solving the flow field during a high-speed train nose entering a tunnel, using the unsteady three-dimensional (3D) Euler equations. After mesh independency and temporal sensitivity tests of the numerical method, validations are conducted by comparing the numerical results with experimental and numerical data. The temporal gradients of pressure wavefront are parametrically investigated for different combinations among the train speed, the blockage ratio of the train to tunnel, and inclination angle of the tunnel entrance. The numerical results show a negligible influence of train Mach number or blockage ratio on the normalized pressure gradient and noticeable effects of inclination angle, location of the train with respect to the median line of a double-tracked tunnel (DT), and the profile of train nose. Based on the numerical results, an empirical formula is proposed to predict the relationship between the maximum pressure gradient and the inclination angle of tunnel entrance.

1209 複数の空力特性から評価した高速列車先頭形状の実験的研究(OS1-2 鉄道の騒音・空力・軌道と航空管制,OS1 交通・物流システムの高速化,利便性,快適性の向上,オーガナイズド・セッション(OS))

1209 複数の空力特性から評価した高速列車先頭形状の実験的研究(OS1-2 鉄道の騒音・空力・軌道と航空管制,OS1 交通・物流システムの高速化,利便性,快適性の向上,オーガナイズド・セッション(OS))

Application of aluminium honeycomb sandwich panel as an energy absorber of high-speed train nose

Since train’s frontal nose is the first part of the train which is damaged at the frontal impact, specific attention should be paid to the design of this part. In this study, an effort has been conducted to the design of a nose with light weight which can absorb maximum amount of energy that is possible during a frontal collision. To this aim and with attention to aerodynamic considerations, application of aluminium honeycomb sandwich panel has been studied. This paper includes two main parts. The first part is dedicated to the simulation of aluminium honeycomb sandwich panel, while the frontal collision of nose with different internal layer thicknesses of honeycomb and various nose lengths have been simulated in the second part. Finite element method using LS-DYNA commercial package has been used for the numerical simulation. The results have been validated with available experimental results and an acceptable agreement has been observed.

Multi-Objective Design Optimization of High-Speed Train Nose

This paper presents a novel design technique for high-speed trains using a multi-objective optimization method to balance plural aerodynamic properties. The technique involves the use of an evolutionary algorithm, a shape parameterization technique that uses B-spline curves and Coons patches, and a computational simulation that uses a Message Passing Interface. To demonstrate the capability of the method, a train nose is designed that has optimized aerodynamic drag and aerodynamic forces with respect to affecting other trains. A 10th generation evolutionary calculation with 512 individuals was conducted, and physically reasonable Pareto solutions were successfully obtained.

Three-dimensional aerodynamic optimization design of high-speed train nose based on GA-GRNN

With the speed upgrade of the high-speed train, the aerodynamic drag becomes one of the key factors to restrain the train speed and energy saving. In order to reduce the aerodynamic drag of train head, a new parametric approach called local shape function (LSF) was adopted based on the free form surface deformation (FFD) method and a new efficient optimization method based on the response surface method (RSM) of GA-GRNN. The optimization results show that the parametric method can control the large deformation with a few design parameters, and can ensure the deformation zones smoothness and smooth transition of different deformation regions. With the same sample points for training, GA-GRNN performs better than GRNN to get the global optimal solution. As an example, the aerodynamic drag for a simplified shape with head + one carriage + tail train is reduced by 8.7%. The proposed optimization method is efficient for the engineering design of high-speed train.

Study on high-speed train nose under frontal and side impact

Frontal and side impacts are both important aspects in designing of a crashworthy high-speed train nose. Therefore a proper design should be considered both conditions and, compatibility should be made among the features that improve train nose crashworthiness under different accident situations at the same time. In order to achieve this goal according to aerodynamic rules there is not many options for changing the external shape of high-speed train nose therefore, a systematic study has been conducted to examine possible strategies to design crashworthy internal structure for the high-speed train nose that provide the best features under both frontal and side impact conditions. For this purpose, various multi-layer noses are studied and the best internal layer geometry is proposed. At the last step effects of foam usage in different spaces between internal and external layers of nose is shown.

Optimal cross-sectional area distribution of a high-speed train nose to minimize the tunnel micro-pressure wave

Optimization of the cross-sectional area distribution of a high-speed train nose is conducted for various nose lengths in order to minimize the micro-pressure wave intensity at a tunnel exit. To this end, an inviscid compressible flow solver is adopted with an axi-symmetric patched grid system. To improve the shape of the train nose, multi-step design optimization is performed using the Broyden---Fletcher---Goldfarb---Shanno (BFGS) algorithm with a response surface model. The optimization reveals that the optimal nose shapes differ for different nose lengths. For a short nose, the shape has an extremely blunt front end, and the cross-sectional area decreases in the middle section. As the nose length increases, the nose shape flattens around the middle section. These optimal shapes divide one large compression wave into two small waves by causing a strong expansion effect between the front and rear ends. As a result, through the nose shape optimization, the intensity of the micro-pressure wave is reduced by 18---27% compared to a parabolic nose, which has a minimum variation of the cross-sectional area change. The optimized distribution of the cross-sectional area can be used as a guideline for the design of three-dimensional nose shapes of high-speed trains, further improving their aerodynamic performance.

Study on characteristics of a crashworthy high-speed train nose

The external shape of a high-speed train nose is usually designed according to the aerodynamic considerations and to minimise the drag forces and noises. Crashworthiness of the nose is another aspect that is important from the passive-safety point of view. To improve the crashworthiness characteristics, usually there are not many options for changing the external shape of a high-speed train nose; therefore, a systematic study has been conducted to examine possible strategies in order to design crashworthy external and internal structures for a high-speed train nose. It is observed that the longer and slender noses show better crashworthiness characteristics. In addition, various multi-layer noses are studied, and the best internal-layer geometry is proposed. At the last step the effects of foam usage in different spaces between internal and external layers of the nose are shown.

Approximate optimization of high-speed train nose shape for reducing micropressure wave

The paper deals with the nose shape design of high-speed railways to minimize the maximum micropressure wave, which is known to be mainly affected by train speed, train-to-tunnel area ratio, slenderness and shape of train nose, etc. It is advantageous to develop a proper approximate metamodel for replacing the real analysis code in the context of approximate design optimization. The study has adopted a newly introduced regression technique; the central of the paper is to develop and examine the support vector machine (SVM) for use in the sequential approximate optimization process. In the sequential approximate optimization process, Owen’s random orthogonal arrays and D-optimal design are used to generate training data for building approximate models. The paper describes how SVM works and how efficiently SVM is compared with an existing Kriging model. As a design result, the present study suggests an optimal nose shape that is an improvement over current design in terms of micropressure wave.

Kriging-based approximate optimization of high-speed train nose shape for reducing micropressure wave

Trains travelling at high-speed into a tunnel generate micropressure waves causing an explosive noise at the tunnel exit. This paper deals with the design of high-speed railways nose shape design to minimize the maximum micropressure wave which is known to be mainly affected by train speed, train-to-tunnel area ratio, slenderness and shape of train nose, etc. It is more efficient to develop a proper approximate meta-model for replacing the real analysis code in the context of approximate design optimization. The study has adopted the Kriging meta-model; the central of the paper is to develop and examine Kriging for use in the sequential approximate optimization process. In the sequential approximate optimization process, Owen's random orthogonal arrays and D-optimal design are used to generate training data for building approximate models. The paper describes how Kriging works and how much it is efficient as an approximation model in the context of approximate optimization. Consequently, the present study suggests the new optimal nose shape that is more improved than currently used design in terms of micropressure wave.