Drag-Reducing Rear Fairings for Tractor Trailers

Abstract

This study investigated the use of airfoils mounted on tractor trailers as a fuel-saving device. Inspired by prior work in the field of aerodynamic improvements for tractor trailers, study used servo-actuated airfoils to influence the wake in an attempt to lessen the pressure drag that dominates fuel consumption at highway speeds. Various configurations of airfoils were tested for their drag characteristics. It was found that although the prototype configurations suggested here rarely achieved lower drag than the baseline (unmodified) model truck, they clarified how certain design parameters, such as mounting height and chord length influenced drag. Several aerodynamic flow regimes were considered as mechanisms of improvement, such as boundary layer manipulation against a hard surface, streamlining vortex shedding by encouraging attached flow, and introducing counter-rotating tip vortices to increase pressure in the wake. From this study, it is not clear that transitioning from at-plate style devices to the novel airfoil configurations makes economic sense. However, the relationships found between the studied design parameters and drag could be applied to future iterations of aerodynamic drag reduction devices.