Aerodynamic Optimization of High-Speed Trains Nose using a Genetic Algorithm and Artificial Neural Network

An aerodynamic optimization of the train aerodynamic characteristics in term of front wind action sensitivity is carried out in this paper. In particular, a genetic algorithm (GA) is used to perform a shape optimization study of a high-speed train nose. The nose is parametrically defined via Bézier Curves, including a wider range of geometries in the design space as possible optimal solutions. Using a GA, the main disadvantage to deal with is the large number of evaluations need before finding such optimal. Here it is proposed the use of metamodels to replace Navier-Stokes solver. Among all the posibilities, Rsponse Surface Models and Artificial Neural Networks (ANN) are considered. Best results of prediction and generalization are obtained with ANN and those are applied in GA code. The paper shows the feasibility of using GA in combination with ANN for this problem, and solutions achieved are included.

Models for Lateral Dynamic Interaction of High-Speed Trains and Bridges

In this work a methodology for analysing the lateral coupled behavior of large viaducts and high-speed trains is proposed. The finite element method is used for the structure, multibody techniques are applied for vehicles and the interaction between them is established introducing wheel-rail nonlinear contact forces. This methodology is applied for the analysis of the railway viaduct of the R´ıo Barbantino, which is a very long and tall bridge in the north-west spanish high-speed line.

Do charges to freight trucks and trains in the European Union reflect their social marginal costs? Application to the case of Spain

In the last few years, the European Union (EU) has become greatly concerned about the environmental costs of road transport in Europe as a result of the constant growth in the market share of trucks and the steady decline in the market share of railroads. In order to reverse this trend, the EU is promoting the implementation of additional charges for heavy goods vehicles (HGV) on the trunk roads of the EU countries. However, the EU policy is being criticised because it does not address the implementation of charges to internalise the external costs produced by automobiles and other transport modes such as railroad. In this paper, we first describe the evolution of the HGV charging policy in the EU, and then assess its practical implementation across different European countries. Second, and of greater significance, by using the case study of Spain, we evaluate to what extent the current fees on trucks and trains reflect their social marginal costs, and consequently lead to an allocative-efficient outcome. We found that for the average case in Spain the truck industry meets more of the marginal social cost produced by it than does the freight railroad industry. The reason for this lies in the large sums of money paid by truck companies in fuel taxes, and the subsidies that continue to be granted by the government to the railroads.

Electrically tunable delay for trains of optical pulses

A technique to implement an electrically tunable delay line with high bandwidth for trains of ultrashort optical pulses is presented. The system is based on the temporal self-imaging effect in fiber gratings and electrooptic modulation.

Criteria for Ballast Flight Initiation Induced by High Speed Trains

One of the phenomena that limit the velocity of trains in high speed lines is the so- called “ballast pick-up”. It is a ballast train-induced-wind erosion (or BATIWE) that can produce damage to the train under body and the infrastructure surrounding the tracks. The analysis of the measurements taken during several passes of the train allows for a criterion of ballast flight initiation to be obtained. The first rotation of a ballast stone occurs when the impulse given to the stone (arising from the aerodynamic loading produced by the wind gust genera ted by the passing train) overpasses a critical impulse. This impulse depends on the physical properties of the stone (mass, shape, moment of inertia, etc. ...) and its posture on the track bed. The aim of this paper is to report on the experimental results obtained in the ADIF’S Brihuega (Guadalajara) test station, in the Madrid to Barcelona high speed line, and the way they can be used to support the feasibility of the definition of a criterion to evaluate the BA TIWE capability of trains. The results obtained show the feasibility of the proposed method, and contribute to a method of BATIWE characterization, which can be relevant for the development of train interoperability standardization.

Great marquee for high-speed trains in the new railway station of Malaga

The commercial centre VIALIA and the new railway station of the AVE (high speed train) in Malaga was inaugurated in November 2006, just on the place of the former railway station. The new railway station with an investment of 134,7 million Euros occupies a surface of 51.377 m2, five times the surface of the former station. The enclosure is the biggest intermodal and commercial centre of Spain which comprises a parking of 21.000 m2 for 1300 parking places, one commercial area and a hotel with a total extension constructed of approximately 100.000 m2. The spaces of leisure contain cinemas, shops, restaurants, bowling, gymnasium, swimming pool and zones of passenger's traffic.

Great roof marquee in the new railway station for high speed trains of Málaga

The new railway station of María Zambrano for AVE (Spanish high-speed trains) located in Malaga, has been inaugurated in November 2006, just on the site of the former railway station. The new railway station with an investment of 134.7 million Euros occupies a surface of 51.377 m2, five times the surface of the former station. The enclosure is the biggest intermodal transport and commercial center of Spain which comprises a parking of 21,000 m2 for 1,300 parking places, one commercial area and a hotel of 35 m height, with a total extension constructed of approximately 100,000 m2.

Trade-off aproaches for the vibroacoustic analysis of trains

Passengers’ comfort in terms of acoustic noise levels is a key design driver for train design. The problem is especially relevant for high speed trains, where the aerodynamic induced noise is dominant, but it is also important for medium speed trains where the mechanical sources of noise may have more influence. The numerical interior noise prediction inside the train is a very comp lex problem, involving many different parameters: complex geometries and materials, different noise sources, com- plex interactions among those sources, broad range of frequencies where the phenomenon is important, etc. In this paper, the main findings of this work developed at IDR/UPM (Instituto de Microgravedad “Ignacio Da Riva”, Universidad Politécnica de Madrid) are presented, concentrat ing on the different modelling methodologies used for the different frequency ranges of interest, from FEM-BEM models, hybrid FEM-SEA to pure SEA models. The advantages and disadvantages of the different approaches are summarized. Different modelling techniques have also been evaluated and compared, taking into account the various and specific geometrical configurations typical in this type of structures, and the material properties used in the models. The critical configuration of the train inside a tunnel is studied in order to evaluate the external loads due to noise sources of the train. In this work, a SEA-model composed by periodic characteristic sections of a high spee d train is analysed inside a tunnel.

Multi-objective Aerodynamic Optimization of High-speed Trains in Tunnels

A genetic algorithm (GA) is employed for the multi-objective shape optimization of the nose of a high-speed train. Aerodynamic problems observed at high speeds become still more relevant when traveling along a tunnel. The objective is to minimize both the aerodynamic drag and the amplitude of the pressure gradient of the compression wave when a train enters a tunnel. The main drawback of GA is the large number of evaluations need in the optimization process. Metamodels-based optimization is considered to overcome such problem. As a result, an explicit relationship between pressure gradient and geometrical parameters is obtained.

Big bridge in pérgola for high speed trains to the northwest of Spain

Big bridge in pérgola for high speed trains to the northwest of Spain

Aeroacoustics in high speed trains

Este trabajo se centra en el estudio de problemas aeroacústicos en los trenes de alta velocidad. Se han considerado dos escenarios en los que las ondas de presión generadas son críticos para el confort de los pasajeros. Uno es el debido a las ondas de presión que genera el tren cuando entra y sale de un túnel, que a su vez producen saltos de presión de baja frecuencia en el tren (cuando se cruzan con él) y en los alrededores del túnel cuando alcanzan la salida. Se estudia este fenómeno, y se propone un sistema aeroelástico basado en el galope transversal para disminuir la energía de estas ondas, y se analiza la energía extraíble de las ondas utilizando cuerpos con diferentes secciones transversales [Sorribes-Palmer and Sanz-Andres, 2013]. La influencia de la geometría de los portales en la energía radiada hacia el exterior de túnel es analizada experimentalmente, prestando especial atención a las boquillas porosas. Las ondas de presión en el interior del túnel se han analizado mediante el método de las características. Se han realizado ensayos experimentales para estimar la energía reflejada hacia el interior del túnel al alcanzar las ondas de presión el portal de salida del túnel. Se ha estudiado la formación e interacción entre el portal del túnel y la onda de choque generada en los túneles de gran longitud y pequeña fricción. Se propone un método para describir de forma aproximada el ruido radiado al exterior. Por otro lado se ha estudiado el ruido de media y alta frecuencia de origen aerodinámico. Se ha estudiado la influencia del desprendimiento de la capa límite sobre el tren. Se propone una metodología basada en una sección de tren característica para predecir rápidamente el nivel de presión de sonido dentro y fuera del tren para todo el rango de frecuencias. Se han realizado medidas experimentales en vía de los espectros de presión sobre la superficie del tren, y de la transmisibilidad de las uniones entre estructura y revestimiento. Los resultados experimentales se han utilizado en los modelos vibroacústicos. El método de la sección del tren característica es especialmente útil a altas frecuencias cuando todo el tren se puede modelar mediante el ensamblaje de diferentes secciones características utilizando el análisis estadístico de la energía. ABSTRACT This work is focused on the study of aeroacoustic problems in high speed trains. We have considered two scenarios in which the pressure waves generated are critical for passengers comfort. The first one is due to the pressure waves generated by a train entering in a tunnel. These waves generate pressure gauges inside the train (when they find each other) and outside of the tunnel portals. This phenomenon has been studied, and an aeroelastic system based on transverse galloping to reduce the energy of these waves is proposed. The maximum extractable energy by using bodies with different cross-section shapes is analyzed. The influence of the portals geometry in the energy radiated outwards the tunnel is analyzed experimentally, with particular attention to the porous exits. The pressure waves inside the tunnel have been analyzed using the method of characteristics. Experimental tests to estimate the energy reflected into the tunnel when the pressure waves reach the tunnel portal have been performed. We have studied the generation and interaction between the tunnel portal and a shock wave generated in long tunnels with small friction. A method to describe in an approximated way the pressure radiated outside the tunnel is proposed. In the second scenario, middle and high frequency noise generated aerodynamically has been studied, including the influence of the detachment of the boundary layer around the train. A method based on a train section to quickly predict the sound pressure level inside and outside the train has been proposed. Experimental test have been performed on board to evaluate the pressure power spectra on the surface of the train, and the transmissibility of the junctions between the structure and trim. These experimental results have been used in the vibroacoustic models. The low frequency pressure waves generated with the train during the tunnel crossing has been identified in the pressure spectrum. The train characteristic section method is especially useful at high frequencies, when the whole train can be modeled by assembling different sections using the statistical energy analysis. The sound pressure level inside the train is evaluated inside and outside the tunnel.

High-speed trains and tourists: what is the link? Evidence from the French and Spanish capitals

The objective of this paper is to analyse the factors influencing tourists? choice of a destination and the role of High Speed Rail (HSR) systems in this choice. The methodology proposed consists in analysing two capitals in Europe, i.e. Paris and Madrid where HSR services are important, to investigate the factors influencing holidaymakers in choosing these cities, and the role of HSR in this choice. The main outcome of this paper is to show that several factors influence the choice of a tourist, like the presence of architectural sites, the quality of promotion of the destination itself, the presence of events, and also HSR services. However we found that the HSR system has affected the choice of Paris and Madrid in a different way. Concerning the French case study, HSR is considered a real transport mode alternative among tourists, therefore HSR is chosen to reach Paris as well as for revisiting it. On the other hand, Madrid is chosen by tourists irrespective on the presence of HSR, while HSR is chosen for reaching cities close to Madrid. Data collected from the two surveys have been used for a further quantitative analysis. Models have been specified and calibrated to identify the factors influencing holidaymakers to revisit Paris and Madrid and the role of HSR in this choice has been highlighted.

Aeroacoustic noise prediction in high speed trains due to attached and detached flow

This paper aims to set out the influence of the flow field around high speed trains in open field. To achieve this parametric analysis of the sound pressure inside the train was performed. Three vibroacoustic models of a characteristic train section are used to predict the noise inside the train in open field by using finite element method FEM, boundary element method (BEM) and statistical energy analysis (SEA) depending on the frequency range of analysis. The turbulent boundary layer excitation is implemented as the only airborne noise source, in order to focus on the study of the attached and detached flow in the surface of the train. The power spectral densities of the pressure fluctuation in the train surface proposed by [Cockburn and Roberson 1974, Rennison et al. 2009] are applied on the exterior surface of the structural subsystems in the vibroacoustic models. An increase in the sound pressure level up to10 dB can be appreciated due to the detachment of the flow around the train. These results highlight the importance to determine the detached regions prediction, making critical the airborne noise due to turbulent boundary layer.

Vibroacoustic Problems in High Speed Trains

Passengers comfort in terms of acoustic noise levels is a key train design parameter, especially relevant in high speed trains, where the aerodynamic noise is dominant. The aim of the work, described in this paper, is to make progress in the understanding of the flow field around high speed trains in an open field, which is a subject of interest for many researchers with direct industrial applications, but also the critical configuration of the train inside a tunnel is studied in order to evaluate the external loads arising from noise sources of the train. The airborne noise coming from the wheels (wheelrail interaction), which is the dominant source at a certain range of frequencies, is also investigated from the numerical and experimental points of view. The numerical prediction of the noise in the interior of the train is a very complex problem, involving many different parameters: complex geometries and materials, different noise sources, complex interactions among those sources, broad range of frequencies where the phenomenon is important, etc. During recent years a research plan is being developed at IDR/UPM (Instituto de Microgravedad Ignacio Da Riva, Universidad Politécnica de Madrid) involving both numerical simulations, wind tunnel and full-scale tests to address this problem. Comparison of numerical simulations with experimental data is a key factor in this process.

Numerical Simulation of the Aerodynamic Behavior of High Velocity Trains under Synthetic Crosswinds of Different Shear and Turbulence Characteristics

A numerical simulation of the aerodynamic behavior of high-speed trains under synthetic crosswinds at a 90º yaw angle is presented. The train geometry is the aerodynamic train model (ATM). Flow description based on numerical simulations is obtained using large eddy simulation (LES) and the commercial code ANSYSFluent V14.5. A crosswind whose averaged velocity and turbulence characteristics change with distance to the ground is imposed. Turbulent fluctuations that vary temporally and spatially are simulated with TurbSim code. The crosswind boundary condition is calculated for the distance the train runs during a simulation period. The inlet streamwise velocity boundary condition is generated using Taylor?s frozen turbulence hypothesis. The model gives a time history of the force and moments acting on the train; this includes averaged values, standard deviations and extreme values. Of particular interest are the spectra of the forces and moments, and the admittance spectra. For comparison, results obtained with LES and a uniform wind velocity fluctuating in time, and results obtained with Reynolds averaged Navier Stokes equations (RANS), and the averaged wind conditions, are also presented.