Flow Analysis between Two Bluff Bodies in a Close Distance Platooning Configuration

This article analyses the flow field between two 1/8-scale Generalized European Transport System (GETS) models which are placed in a two-vehicle platoon at close distances. Numerical simulations using the lattice Boltzmann method together with a wind tunnel experiment (open jet facility, OJF) were executed. Next to balance measurements, coaxial volumetric velocimetry (CVV) measurements were performed to obtain information about the flow field. Three intervehicle distances, 0.10, 0.45 and 0.91 times the vehicle length, were tested for various platoon configurations where the vehicles in the platoon varied in terms of front-edge radius and the addition of tails. At the smallest intervehicle distance, the greatest reductions in drag were found for both the leading and trailing vehicles. The flow in the gap between the two vehicles follows an S-shaped path with small variations between the configurations. For the second distance, the leading model still experiences a decrease in drag however smaller compared to the closest distance. For the trailing model either a drag increase or decrease is found depending on its front-edge radius. The addition of a tail to the trailing model always benefits the drag reduction, while applying a tail to the leading model can be both beneficial and disadvantageous to the drag of the trailing model depending on the tail angle. At this distance the wake of the leading model resembles that of the isolated model. Due to the vortex shedding of the leading model, large force fluctuations are seen for the trailing model. At the largest distance the drag decrease for the leading model is in the order of a few percent; while for the trailing model this again depends on the front-edge radius. At this largest separation distance, the wake of the leading model has returned to that of the isolated model.