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.
This work presents aerodynamic results of crosswind stability obtained numerically and experimentally for the leading control unit (class 808) of Deutsche Bahn AG's high-speed train Inter-CityExpress 2. The train model is on top of a 6 m high embankment in accordance with the proposed European code for interoperable trains, the so-called technical specifications for interoperability. The purpose of the study is to convey the predictive accuracy that typical steady-state computational fluid dynamics-Reynolds average Navier-Stokes methods (industry standard) return and to contribute to the understanding of the aerodynamics for the current application.Attention is drawn to the aerodynamics around the train and embankment when subjected to a steady block profile crosswind of 30 • yaw angle on the basis of the onset velocity far upstream the embankment. The Re (Reynolds number) of the embankment cases is 4.6 × 10 6 . Calculated results are obtained with the commercial code STAR-CD, with exclusively hexahedral meshes with a total cell count of 13.5 × 10 6 . Results are obtained when the train stands on the windward and leeward tracks on top of the embankment. These results are first compared with a flat ground case from a previous study.Then experimental data are obtained in a high-pressure wind tunnel with a model scale of 1:100. Re effects are compensated by raising the ambient pressure by a factor of 60, which increases the air density and thus the Re by a similar factor. Calculated results are in fair agreement with the experiments, where both the calculations and the experiments predict the leeward case to be the more critical one.In addition, the related consequences on the mechanical behaviour, i.e. the stability of the car, are briefly addressed by means of a quasi-static mechanical analysis. The results of the present study indicate that the 6 m high embankment concerning the current train reduces the permissible crosswind speed with approximately 20 per cent.
An ICE 3 model has been investigated in an automotive wind tunnel on three different ground configurations by means of force measurements and tuft flow visualisations. The aerodynamic force and moment coefficients reveal a strong dependency on the ground configuration, with the embankment configuration giving the highest measured coefficients only for yaw angles β < 40• . The coefficients obtained through the Baker hypothesis are found to be larger than those measured directly on the embankment. The poor agreement between the "measured on embankment coefficients" and the "flat ground with Baker transformation coefficients" is attributed to the fundamental mismatch of relative flow velocities between wind, train and ground during the wind tunnel measurements with the train situated on the embankment. The mismatch of flow velocities causes a strong longitudinal vortex on on the leeward side of the embankment which does not exist in reality and significantly alters the overall flow field. It is thus recommended, for the determination of aerodynamic forces acting on a train on an embankment, to measure the aerodynamic coefficients for the flat ground configuration and subsequently apply the Baker hypothesis.
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