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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.

MIRA worked with JCB and Ron Ayers for thirteen months on the aerodynamic development of the JCB DIESELMAX diesel land speed record vehicle prior to it achieving all its targets on the 23rd of August 2006 when it smashed the FIA record, setting a new mark of 350.092mph. A decision was made at the beginning of the project to use Computational Fluid Dynamics (CFD) as the primary aerodynamic development tool due to the difficulties in testing a nine metre long vehicle at 350mph in a wind tunnel. Following five design phases and a total of twenty four runs the drag coefficient (CD) was reduced to 0.147, with total lift coefficient at -0.141 and a near perfect 48/52 downforce balance.