Modelling of efficiency of aerodynamic devices on a tractor-trailer

Abstract

While trucking accounts for 60% of freight energy use in the US, aerodynamic drag is responsible for 65% of the total energy expenditure for a heavy truck at 70 miles per hour. Reducing the aerodynamic resistance of a heavy truck can significantly improve its fuel economy. While multiple aerodynamic devices have been proposed for heavy trucks, they do not always promote the most efficient operation, as they may hinder manoeuvring and docking. This limited acceptance by the industry can be summarised as a contradiction: aerodynamic devices are useful at cruising speed, but during docking or manoeuvring, they may be an obstacle to efficient operations. This contradiction can be resolved if the devices are only deployed or interact with the incoming flow at high speed. Examples are dynamic (foldable) side fairings and vortex generators (VGs). Computational fluid dynamics (CFD) modelling of the VGs under head and side wind conditions has shown that they are more efficient for side winds than for head winds.