Aerodynamic investigations of the effects of virtual coupling on two next generation trains

Abstract

This paper presents the results of force measurements on a tandem configuration (platoon) of two train models (Type: Next Generation Train) at varying distances in heading direction in the water towing tank at the German Aerospace Center Göttingen (DLR). The trains had no mechanical connection to represent the occurring situation of virtual coupling. The experiments were conducted at a Reynolds number of 240,000 at 4, m/s. A ground plate was used to account for under floor effects. The gap distance was varied between 1.2% and 59.5% of the single train length. In comparison to a single vehicle, drag reductions of up to 30.4% were observed for the trailing vehicle at all distances. For the leading train reduced resistances at distances ≤12% were found. The combined drag of two vehicles is up to 16% less than the resistance of two single trains. With Particle Image Velocimetry (PIV) a strong interaction between both trains is observed at closest distance (1.2%). An area of reduced relative velocity and thus reduced stagnation pressure in front of the second train is found to be the reason for a smaller drag. At wider gaps (35.7% and 47.6%) a beneficial development of vorticity behind the first train is found to be the cause of a reduced drag value on the trailing vehicle.