EUROMECH COLLOQUIUM 509 Vehicle Aerodynamics External Aerodynamics of Railway Vehicles, Trucks, Buses and Cars Berlin, Germany, March 24–25, 2009 QUALITATIVE INVESTIGATION OF THE MAIN FLOW FEATURES OVER A TGV Thomas Duriez ⋆† , Jean-Luc Aider ⋆ , Elisa Masson † and Jose E. Wesfreid ⋆ ⋆ Laboratoire Physique et Mécanique des Milieux Hétérogènes (PMMH) CNRS UMR 7636; ESPCI; Paris6; Paris7 ESPCI, 10, rue Vauquelin, 75231 Paris cedex 05, France e-mail: aider@pmmh.espci.fr † Unité Physique du Système Ferroviaire SNCF - Direction de l’Innovation et de la Recherche, 45 rue de Londres, 75379 Paris Cedex 08,France e-mail: elisa.masson@sncf.fr, Keywords: High-Speed Trains, Visualisations, PIV Abstract: In this paper, we present the results of a preliminary investigation of the flow features encountered over a TGV. As a matter of fact, it is the first step in a more detailed analysis which is necessary in the perspective of future flow control experiments. The experimental investiga- tion has been carried out in a low-speed hydrodynamic channel with a small-scale model. The consequence is that the Reynolds number based on the length L of the model is relatively low (Re L =1.26 10 5 ) compared to the full-scale aerodynamic Reynolds number (Re L = 10 9 ) so that the results can only be used as qualitative tools to illustrate the main features encountered in the flow over a TGV. Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) visualizations were carried out in most of the critical regions over a TGV: the front nose, the pantograph cavity, the spacings between the coaches and the rear part of the model. Clearly some common features can be found with the flow over a road vehicle. For instance, both LIF and PIV show the strong vortex shedding, the large recirculation bubble and the large counter-rotating vortices created over the rear part of the model, very similar to a Ahmed body with a 25 ◦ rear slant. The flow over the flat panels of the coaches constituting the TVG is also more complex than expected because of the perturbations induced by the pantograph cavities and the deep cavity between the coaches. Finally, a synthesis is proposed pointing out the most critical areas in a perspective of flow control for drag reduction. 1