Nicolas Paradot

Cross-wind effects on road and rail vehicles

This paper presents a review of recent research that has been carried out on the cross-wind effects on road and rail vehicles. After a brief introduction to the issues involved, the risk analysis framework is set out. All risk analysis methods require some knowledge of cross-wind aerodynamic force and moment coefficients, and methods of obtaining these through full scale and wind tunnel testing and through Computational Fluid Dynamics methods are then described. The picture of the flow fields around vehicles that is suggested by these measurements and calculations is then presented, and the steady and the unsteady aerodynamic force characteristics described. The detailed methodology for using this information to predict accident risk is then set out, including details of the vehicle dynamics system models that can be used. Finally potential alleviation methods are described and suggestions made for further works.

The Numerical Prediction of the Aerodynamic Noise of the TGV POS High-Speed Train Power Car

For a high-speed train operating at 300km/h or more, the aerodynamic noise, which is induced by the pressure fluctuations of the air, reaches similar levels to the rolling noise, which is due to contact between the rail and wheel. For this reason, the study of the noise generated by the flow around the train is of great interest for the constructors and operators of high-speed trains. Although the main noise sources are now well identified, their localization is so far mainly based on experimental techniques using acoustic array measurements, applied either on small-scale models in a wind tunnel or on full-scale passing trains. Nonetheless, the numerical prediction of the aerodynamic noise is becoming more and more of a practical possibility, as the need is emerging for proper integration of technical solutions and optimizations at an early stage of design of new rolling stock.

Crosswind sensitivity assessment of a representative Europe-wide range of conventional vehicles

The European Union Seventh Framework Programme research project AeroTRAIN aimed at delivering limit criteria for crosswinds to the ‘Rolling stock – locomotives and passenger rolling stock’ Technical Specification for Interoperability (CR LOC&PAS TSI) and for class 2 trains of the high-speed rolling stock TSI (HS RST TSI). A first objective was the assessment of characteristic wind curve (CWC) for identified class 2 and conventional vehicles with low, but sufficient, crosswind stability (as proven by their safe operational records) on the EN 14067-6: 2010 single track with ballast and rails (STBR) standard configuration. In the same manner, and as a second objective, Reference CWC and limit criteria for class 1 trains of HS RST TSI were planned to be determined. For all these trains, the aerodynamic coefficients were obtained in a unique wind tunnel campaign using the STBR ground configuration. Their crosswind sensitivity was assessed against a calculated CWC obtained from vehicle dynamics simulations. The resulting database will allow the derivation of the relevant limit criteria still needed for vehicle authorization regarding crosswind stability.

A risk assessment method for ballast flight; managing the rolling stock/infrastructure interaction

The evaluation of the level of risk resulting from the phenomenon of ballast flight is currently receiving considerable attention, due to its direct impact on the safety and reliability of commercial railway operations. Of particular interest are the effects of this phenomenon on both railway infrastructure and rolling stock. It is difficult to analyse the ballast flight phenomenon, due to its dependence on a large number of variable parameters. Investigations carried out at SNCF have led to the proposal of a global approach, called the stress–strength interference analysis method, which can be applied by considering a relevant indicator to evaluate the risk due to flying ballast. This paper presents the work on the application of the proposed analysis approach to the ballast flight phenomenon performed within the FP7 EU AeroTRAIN project. The approach considers the influence of the passage of dedicated rolling stock and the resistance of the track to the displacement of ballast. It leads to the proposal of a methodology to evaluate the risk of ballast flight in high-speed rail operations; this allows the evaluation of the degradation rate of railway infrastructure and rolling stock due to this phenomenon to be performed.

Numerical Simulation and Experimental Investigation of the Side Loading on a High Speed Train

An assessment of train safety whilst simultaneously traveling at high speed and being subjected to strong cross winds requires the knowledge of the aerodynamic load on the train. This situation currently affects the French high speed double decker train (TGV Duplex) that travels on the “TGV Mediterranee” line between Paris and Marseille. For safety reasons, the SNCF has investigated the cross wind sensitivity of the TGV Duplex operating on this line using both reduced scale wind tunnel and hydraulic tank tests and numerical methods. Comparisons between experimental and numerical side and lift forces and lee rail rolling moments acting on the TGV have been made. The leading vehicle experimental pressure distributions have also permitted further comparisons between the experimental and numerical results. Overall, these comparisons showed good agreement between the two sets of results for TGV / wind relative flow angles of 30° or less. Beyond this, the differences between the results are more pronounced with a maximum difference occurring for a relative flow angle of approximately 60°.