Effect of the Frontal Edge Radius in a Platoon of Bluff Bodies

This paper investigates the effect of the frontal edge radius of the Generalized European Transport System (GETS) model on the aerodynamic behavior of three different vehicles in a platoon. Due to the increasing awareness around harmful gases and depleting oil sources, more sustainable transport systems are needed. The efficiency of long-haul, heavy-duty vehicles can be increased by driving in platoon formation in order to decrease aerodynamic drag and to increase fuel mileage. The drag behavior of drafting vehicles is already studied but differences in aerodynamic drag reductions occur on the trailing vehicle. Some studies indicate a drag increase while others predict a drag decrease. In this study, a numerical investigation was performed solving Reynolds Averaged Navier-Stokes equations with the aid of a commercial package. Four different inter-vehicle distances were tested for the vehicles with several different frontal edge radii. The simulations were validated using wind tunnel experiments on an isolated GETS model. The drag of the lead vehicle showed an asymptotic behavior, increasing towards the value in isolation when the inter-vehicle distance is increased. The drag of the trailing vehicle showed very different behavior. The frontal edge radius was critical in determining the drag increase or decrease of the vehicle. Due to the platoon, the drag of the front part of the trailing vehicle was increased when the frontal edge radius was small. This lead to a total drag increase for the trailing vehicle at specific inter-vehicle distances.