Etude de l'aérodynamique des trains en situation de vents traversiers : impact de la présence d'appendices

Abstract : When expoecd to strong crosswinds, railway trains experience aerodynamic loads which tend to overturn them. The evaluation of the risk of overturning can be done with a dynamic calculation based on the aerodynamic loads and more precisely on the rolling moment. The aerodynamic characteristics of the vehicles can be evaluated in windtunnels. The Reynolds number of a full scale train is not applicable in these tests. Experimental tests showed that a reproduction of the train surface details at the same scale as the model would not necessarily lead to a correct estimation of the real aerodynamic loads.The topic of this work is to investigate the effect of roof mounted cables on the aerodynamic characteristics of railway vehicles. The aim is to determine the influence of the reproduction scale of these appendices on the aerodynamic coefficients. Two train models are employed. The first one is an extensively-studied simplified train model. The second one is more similar to a real train, modelled after a regional train. Visualisation tools are employed to investigate the flow topology. Global aerodynamic loads (lift, lateral force and rolling moment) are evaluated with a dynamometric force balance and surface pressure distribution is evaluated with pressure sensors. Additional RANS numerical simulations are performed to improve understanding of the flow topology.We demonstrated an increase of the risk of overtum for the two train models when cables are added on the roof. We also showed that this increase strongly depends on the cable's size.To understand this increase, we identified pressure modifications which are involved in the global load modifications. Then, we linked these pressure changes to flow topology. We finally showed that the incrcase of the risk of overtun is both due to local and global pressure modifications.
Keywords : Crosswind
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Submitted on : Wednesday, December 16, 2015 - 10:32:08 AM
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Frédéric Deliancourt. Etude de l'aérodynamique des trains en situation de vents traversiers : impact de la présence d'appendices. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2015. Français. ⟨NNT : 2015ESMA0013⟩. ⟨tel-01244699⟩



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