Many studies have been carried out to optimize the aerodynamic performances of a single car or a single vehicle. In present days the traffic increases and sophisticated technologies are developing to guarantee the drivers safety, to minimize the fuel consumption and be more environmentally friendly. Within this research area a new technique that is being studied is Platooning: this means that different vehicles travel in a configuration that minimizes the aerodynamic drag and therefore the fuel consumption and the longitudinal space. In the present study platoons with different vehicles and configurations are taken into account, to analyze the influence of car shape and relative distance between the vehicles. The research has been carried out using CFD techniques to investigate the different flow fields around different platoons, while wind tunnel tests have been used to validate the results of the CFD simulations. The results show that vehicles with an estate back, like station wagons and sport utility vehicles, give a drag reduction up to more than 50% when running in platoon, while vehicles with a fast back, like sedan, that have better performances than sharp-back cars when running isolated, cannot reach the highest drag reduction obtained by the estate back cars. Trucks show negligible drag reduction when running in platoon with other cars, while the vehicles behind the truck experience a very low drag force. The distance between vehicles plays a very important role since smaller distances between the cars give lower aerodynamic forces, and may be minimized only by developing better technologies to control and maintain the position of the vehicle in the platoon without any risk for the passengers.
