Influence of Yaw and Lateral Offset on the Aerodynamics of a Two-Truck Platoon

Governmental regulations and customer demand for more energy-efficient vehicles are driving the development of new solutions in the automotive sector. One way of improving energy efficiency is by reducing the aerodynamic drag. A possible solution to achieve this is the concept of vehicles driving in close proximity, which is now becoming feasible considering the advances in vehicle automation and communication. This study focuses on the behavior of aerodynamic forces and flow effects in a two-truck platoon when more realistic road conditions, such as lateral offset and yaw, are present. The study is primarily numerical, but the results are validated against an experimental campaign conducted earlier by the authors. The main findings are that the drag of the leading truck is mostly governed by the base pressure of its trailer and that the truck sees only minor changes when a lateral offset is added, except at very short intervehicle distances. For larger yaw angles, the leading truck sees an increase in the effective yaw angle for the trailer, resulting in lower efficiency of the platoon. The behavior of the trailing truck is much more complex, with several different effects being observed when yaw and lateral offset are added. When yaw is added, the movement and increased intensity of the stagnation region adds to drag, while the change in effective yaw angle lowers the drag of the vehicle. This causes the benefit of platooning to vary with both yaw angle and vehicle distance. The addition of a lateral offset in the leeward direction can partially compensate for the negative effects of yaw on drag.