Today’s demand for reducing the fuel consumption of vehicles is one of the most challenging issues within the automotive industry. Together with the increased fuel price, the development of more fuel-efficient vehicles is escalating. A recent research about fuel reduction technologies for trucks states that aerodynamic improvements of the tractor unit and the semi-trailer, and thereby drag reduction, is one of the most important technologies for fuel saving.
The research shows that the largest effects of the trailer devices are achieved during 5° yaw, this especially applies for the undercarriage treatment. Furthermore, devices that were implemented in the undercarriage and base region presented the best results, which indicates that these regions are most susceptible to drag improvements.
Aerodynamic drag consists of two components, pressure drag (force acting normal to surface) and friction drag (force acting tangentially to surface). Friction drag is due to shear stress between the fluid and the surface, whereas pressure drag is due to a pressure difference between the front and the rear of the body. For a truck and other blunt bodies, the pressure drag contributes to more than 90 percent of the total drag. In addition to the tractor front, the regions that represent the main drag-contributing areas around a truck are the gap between the tractor and the trailer, the base wake behind the trailer and the undercarriage.
Different types of roof deflectors, side deflectors, and chassis fairings are some good examples of aerodynamic improvements that possible to reduce fuel consumption.