Aerodynamic drag reduction of class 8 heavy vehicles: a full-scale wind tunnel study

A wind tunnel investigation is conducted to evaluate the performance of both commerciallyavailable and prototype aerodynamic drag reduction devices for modern class 8 heavy vehicles. Drag force measurements are made on three full-scale, heavy vehicle configurations at a Reynolds number of 4.6× 10 based upon the vehicle width. The wind-averaged drag coefficient is calculated from the wind tunnel measurements and used to estimate the fuel savings afforded by individual and combinations of devices. For the tractor-trailer gap, the most effective modification is found to be reducing the gap size. Numerous trailer skirts are installed on the three heavy vehicle configurations and the resulting change in the windaveraged drag coefficient is shown to have a nominally linear dependence upon the change in the trailer skirt area. The trailer base drag is alleviated through the installation of boattail devices. When used in combination, the devices often provide a reduction in drag that is greater than the individual contribution from each device. For the best vehicle configurations, the wind-averaged drag coefficient and the resulting estimated fuel use decrease by 0.097 to 0.150 and approximately 10000 to 15000 L per 2.012×10 m of highway mileage driven, respectively.