Calibration of CFD Methods for drag prediction under unsteady on-flow in the DLR SWG Wind Tunnel

Kurzfassung

DLR NGT-Cargo [1] is a logistics concept using rail as the central mode of freight transport. The concept requires the development of competitive transport systems with respect to operational and associated ecological costs. Within this framework an accurate assessment of the aerodynamic drag under realistic vehicle operating conditions is essential. The air flow about a train is characterized by a large range of energetically significant flow scales which challenge accurate numerical simulation, however CFD methods for certification of trains are now accepted with some restrictions by the transport industry. For example, the EN 14067-6 [2] standard permits evaluation of aerodynamic forces by means of computational fluid dynamics (CFD) simulation for full-scale or reduced model geometries under constant cross-wind conditions. At the present time there are no acknowledged international standards concerned with CFD drag prediction under unsteady on-flow conditions for rail vehicles. It is therefore useful to develop sufficiently accurate CFD models to assist in the study of these flows, particularly with respect to operational cost and safety requirements.