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

Abstract

DLR NGT-Cargo [1] is a logistics concept using rail as the central mode of freight transport. This 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. Air flows about trains are characterised 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. However 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 vehicles, particularly with respect to operational cost and safety requirements. This paper extends previous work assessing the ability of CFD to reproduce the aerodynamic drag of a wind tunnel train model under unsteady on-flow conditions.