Because of the rough nature of the truck’s underside, it is beneficial to avoid an excessive amount of air flow and divert the accelerated high-speed flow to the sides of the vehicle instead. This is the function of the optimised front spoiler, while also allowing for adequate ground clearance.
The purpose of the air deflectors is to steer oncoming air flow away from the front edges of the trailer, and create a smooth transition between the tractor and the trailer, with flow being close to the surrounding air flow velocity. The corner area of the deflectors has been given particular attention and been further optimised.
Wheel arch area
The wheel house area is a key source of aerodynamic loss, since the highly turbulent, swirling flow of low speed from the rotating wheel meets the higher velocity laminar structure of the flow outside. In order to minimise these losses, wheels and wheel house perimeters are better matched to optimise each set of wheels.
The purpose of mudguards and mud flaps is to protect other vehicles from water spray when driving in wet conditions. However they are also a source of aerodynamic losses. They should only be wide enough to fulfil their function. The image above shows how high velocity air streaks pass this area. By optimising mudguard and mud flap width, fuel economy can be improved.