The effect of gap width on the aerodynamic drag of a cab-over-engine tractor-trailer combination has been investigated for full-scale gap widths ranging from 0.61 m (24 inches) to 1.83 m (72 inches) over a yaw angle range of 0 to 20 degree. The average drag on the vehicle was found to increase from 0 to 12 percent as the gap width increased from 0.61 m to 1.83 m. Drag reductions were found when a vertical seal was placed along the vehicle centerline between the tractor and the trailer. The effect of vehicle configuration on gap seal effectiveness was evaluated for a gap width of 1.3 m (51 inches) using models of six different tractors and two different trailers. The average drag coefficient reductions that were found ranged from 0.04 to 0.09 with 75 percent of the data being either 0.05 or 0.06. It is shown that the use of gap seals on the nearly half-million vehicles which comprise the nation's long-haul trucking fleet can result in the conservation of about 1.7 X 10 to 9th power liters (0.5 X 10 to 9th power gal) of motor fuel each year.
Samenvatting