Effects on the Aerodynamic Characteristics of Vehicles in Longitudinal Proximity Due to Changes in Style

The potential benefit for vehicles travelling in ‘platoon’ formations arises from a reduction in total aerodynamic drag which can result from the interaction of bluff bodies in close-proximity. During the 1980s this was considered as an opportunity to alleviate congestion and also for fuel-saving in response to the fuel crises of the 1970s. Early interest was limited partly due to the level of available control technology. But recent developments in vehicle-to-vehicle communication systems and autonomous driving technologies have provided the potential for platooning to be incorporated within future traffic management systems prompting renewed interest. For the investigation described in this paper, a new passenger car model was designed as the basis for determining the effectiveness of future low-drag styles in platoon formations. Small-scale models were tested in the Coventry University Wind Tunnel in platoons of up to 5 vehicles. It was found that, for the ‘streamlined’ profile, drag penalties occurred for all vehicles in the platoon configurations compared to a single model of this style when tested alone. Thus the current process within the automotive industry of the optimisation of single vehicles for low-drag might reduce or even negate the possibility to benefit from travelling in close-proximity. In order to give a wider range of efficient operating conditions, future vehicles may require active aerodynamic features or morphing capabilities which could be optimised for proximity effects and matched to shapes of adjacent vehicles. In order to assess this opportunity, tests were also conducted with platoon combinations which included morphed surfaces of the baseline style. Significant drag benefits were found when matching vehicle shape to specific positions in platoons. The work reported in this paper was conducted as part of research to assess the implications and opportunities for a Styling contribution to the aerodynamic characteristics of passenger vehicles operating in close-proximity.