An Investigation of the Inter-Vehicle Distances and Lateral Offsets on Aerodynamic Forces and Wake Structures of Vehicles Platooning

<div class="section abstract"><div class="htmlview paragraph">In traffic scenarios, the spacing between vehicles plays a key role, as the actions of one vehicle can significantly impact others, particularly with regards to energy conservation. Accordingly, modern vehicles are equipped with inter-vehicle communication systems to maintain specific distances between vehicles. The aerodynamic forces experienced by both leading vehicles (leaders) and following vehicles (followers) are connected to the flow patterns in the wake region of the leaders. Therefore, improving our understanding of the turbulent characteristics associated with vehicles platooning is important. This paper investigates the effects of inter-vehicle distances on the flow structure of two vehicles: a small SUV as the leader and a larger light commercial van as the follower, using a Delayed Detached Eddy Simulation (DDES) CFD technique. The study focuses on three specific inter-vehicle distances: S = 0.28 L, 0.4L, and 0.5L, where S represents the spacing between the two vehicles and L is the length of the leader. Realistic flow conditions are simulated with an average velocity of 31.3 m/s. A comprehensive analysis is conducted by studying the influence of various yaw angles: 0°, -3° and -6°, each representing the vehicle’s alignment with the flow, and effects of 0.33m and 0.66m vehicles’ offsets. This study represents the correlation between the vehicle’s orientation and the aerodynamic forces.</div><div class="htmlview paragraph">The findings indicate the unique flow characteristics at various inter-vehicle distances. These results are then compared to a scaled model tested in a wind tunnel at different inter-vehicle distances. The study demonstrates that changing the vehicle distance results in variations in the length of the recirculation region and flow characteristics behind the vehicles, subsequently impacting the drag and lift coefficients of the leader and the follower. In addition, within a specific range of vehicle distances, the two vehicles can benefit from platooning in terms of drag reduction and consequently less energy consumption. The study also investigates the drag coefficients of both the leader and follower at different yaw angles and vehicles’ offsets. The results highlight that drag coefficients increase at higher yaw angles. Furthermore, the paper shows the distributions of mean velocity, static pressure, turbulence characteristics and 3D vortical structures around the leader and the follower. These results provide valuable information of the complex flow behavior and improve our understanding of the aerodynamic forces around the vehicles during platooning. Such information helps the ongoing efforts to optimize vehicles’ energy consumption.</div></div>