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A wind tunnel experimental research program was conducted on a heavily instrumented Ground Transportation System (GTS) vehicle. The GTS baseline model represented a generic 1:8 scale Class-8 van-type tractor trailer geometry. Five base drag reduction add-on devices, instrumented with surface pressure ports, were also tested. These add-on devices included two ogive boattail shapes and three slant geometry devices. Six component force and moment data, surface pressure contours, and wake velocity surveys are presented for each configuration along with qualitative insights gained from flow visualization. This wind tunnel program was designed to complement a parallel research effort in computational fluid dynamics (CFD) which modeled many of these same vehicle geometries. The wind tunnel data are documented and archived in ASCII format on floppy discs and available to researchers interested in further analysis or comparison to other CFD solutions.

The focus of the research was to investigate the fundamental aerodynamics of the base flow of a tractor trailer that would prove useful in fluid flow management Initially, industry design needs and constraints were defined This was followed by an evaluation of state-of-the-art Navier-Stokes based computational fluid dynamics tools Analytical methods were then used in combination with computational tools in a design process Several geometries were tested at 1 8 scale in a low speed wind tunnel in addition to the baseline geometry, base add-on devices of the class of ogival boattails and slants were analyzed

At 70 miles per hour, overcoming aerodynamic drag represents about 65% of the total energy expenditure for a typical heavy truck vehicle. The goal of this US Department of Energy supported consortium is to establish a clear understanding of the drag producing flow phenomena. This is being accomplished through joint experiments and computations, leading to the intelligent design of drag reducing devices. This paper will describe our objective and approach, provide an overview of our efforts and accomplishments related to drag reduction devices, and offer a brief discussion of our future direction.