Keywords: wind-break fences, cross wind, railway lines, computational fluid dynamics analysis, wind tunnel tests.

The determination of the running safety of high speed trains involves the evaluation of the overturning risk associated with crosswind aerodynamic forces. The usual approach to lower the overturning risk is the reduction of the aerodynamic loads through the reduction of the running speed of the train on lines where strong winds occur. This methodology is based on the definition of the characteristic wind curves that define the maximum allowable vehicle speed depending on the wind speed and direction on each particular section of the line. Another method is the installation of wind-break fences on the line in order to reduce the lateral component of the relative wind incoming on the train.

This study uses a numerical computational fluid dynamics (CFD) tool to predict the shielding effect of wind break fences on an ETR500 high speed train. The analysis of the aerodynamic performances of the train is conducted by varying some design parameters of the wind-breaks such as the height of the barrier, the fence porosity and the inclination of the barrier slots. Some wind tunnel tests have been completed in a 1:15 scale at the Politecnico di Milano wind tunnel in order to make a comparison between the numerical and the experimental results.

The shielding effect has been evaluated by analyzing the aerodynamic forces acting on the train. The measurements and the numerical calculations have been conducted varying the wind incidence direction in order to simulate the relative angle of attack on the train.

The results show that the porosity of the wind-break plays a significant role in the shielding performance: the result is relatively independent on the disposition of the slots, since the performance of barriers with uniform and concentrated slots present similar values. This achievement is important since it gives some freedom to the structural designers. On the other hand the inclination of the barrier slots has only minor secondary effects on the shielding of the train.

The numerical simulation results have a good correspondence with the wind tunnel data for all values, with some differences in the evaluation of the vertical force. The magnitudes of the differences are very small and hence the influence on the rolling moment of the train is limited and it does not affect the overturning risk for the train.

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