Preliminary CFD Validation of Unsteady Onflow Effects on Model Train Drag

The DLR New Generation Train Cargo concept (NGT-Cargo) aims to increase the rail share of the European freight traffic market. Computational Fluid Dynamics (CFD) is a useful tool in analyzing high-speed operations which are an important part of this concept. The development of aerodynamic forces under unsteady on-flows should be analyzed within the context of industrial standards, for example guidelines are provided for CFD assessments at cross-wind conditions using the RANS (Reynolds-averaged Navier-Stokes) equations. A major challenge arises because the multi-scale nature of these flows are characterized by a large range of energetically significant flow scales. Wind-tunnel measurements, focused on the development of the aerodynamic forces acting on a train, are being currently performed on a 1:25 scaled NGT model in the cross-wind facility Seitenwindversuchsanlage Göttingen (SWG) located at the DLR Göttingen. This paper presents preliminary work assessing the ability of CFD to reproduce both the observed on-flow conditions as well as the aerodynamic drag of the vehicle.