Wind Tunnel Evaluation of Potential Aerodynamic Drag Reductions from Trailer Aerodynamic Component Combinations

The use of devices to reduce aerodynamic drag on large trailers and save fuel in long-haul, over-the-road freight operations has spurred innovation and prompted some trucking fleets to use them in combinations to achieve even greater gains in fuel-efficiency. This paper examines aerodynamic performance and potential drag reduction benefits of using trailer aerodynamic components in combinations based upon wind tunnel test data.

Representations of SmartWay-verified trailer aerodynamic components were tested on a one-eighth scale model of a class 8 sleeper tractor and a fifty three foot, van trailer model. The open-jet wind tunnel employed a rolling floor to reduce floor boundary layer interference. The drag impacts of aerodynamic packages are evaluated for both van and refrigerated trailers. Additionally, the interactions between individual aerodynamic devices is investigated. Results indicate that combinations of devices can provide trailer aerodynamic drag reductions of up to twenty one percent in wind-averaged conditions. Van and refrigerated trailer configurations show relatively similar aerodynamic performance with refrigerated trailers seeing greater drag reductions in certain cross-wind conditions. The combinations investigated in this study indicate that trailer aerodynamic components can act synergistically, especially in certain cross-wind conditions, providing aerodynamic benefits greater than the sum of their individual impacts. Future study needs are explored.