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Aerodynamics plays an important role in marketing vehicles especially with the recent increases in gas prices. The aerodynamics of one of the widely used vehicle classes (pickup trucks) is examined. The focus is to investigate the effect of the pickup truck configuration on the structure of the airflow around the vehicle and ultimately on the generated aerodynamic drag. The study includes CFD simulations performed using STAR CCM+ developed by CD-Adapco Inc. and full-scale wind tunnel testing conducted in the Langley Full Scale Tunnel (LFST) located at the NASA Langley Research Center but operated by Old Dominion University. The studied pickup truck configurations include a simplified model (no sidewalls or tailgate) and tailgate-off, tailgate-down, and tailgate-up. In all the CFD simulations a generic geometry of an extended cab pickup truck is used. The results indicate that there is a large separation region downstream of the cab and that it controls the aerodynamic drag.

This paper reports on an exploratory automotive test which was undertaken in the NASA Langley Research Center 14 by 22 wind tunnel in the Fall of 2003. The test was collaboration between Old Dominion University, who supplied the automotive balance, NASA, who provided wind tunnel time, and Penske Racing South, who provided an instrumented test vehicle. The test generated a rather unique data set, encompassing whole body forces, surface pressures, and floor boundary layer profiles, measured on the same test article, with both an open jet and closed jet test section, utilizing the variable configuration of the 14 by 22. The nominal test velocity was 60 m/s, the nominal blockage was 7.4%, and the yaw angle ranged from −6 to +6 degrees. Results indicate substantial interference effects, as expected, with around 19% higher drag (uncorrected) in the closed configuration, relative to open. The corresponding front and rear downforce values were 14% and 13% higher respectively.

Aerodynamic testing of heavy commercial vehicles is of increasing interest as demands for dramatically improved fuel economy take hold. Various challenges which compromise the fidelity of wind tunnel simulations must be overcome in order for the full potential of sophisticated aerodynamic treatments to be realized; three are addressed herein. First, a limited number of wind tunnels are available for testing of this class of vehicle at large scales. The authors suggest that facilities developed for large or full-scale testing of race cars may be an important resource. Second, ground simulation in wind tunnels has led to the development of Moving Ground Plane (MGP, aka Rolling Road (RR)) systems of various types. Questions arise as to the behavior of MGP/RR systems with vehicles at large yaw angles. It can actually be deduced that complete simulation of crosswind conditions on an open road in a wind tunnel may be impractical.

The issue of ground simulation in wind tunnels has led to the development of Moving Ground Plane (MGP, aka rolling road) systems of various types. Motorsports aerodynamics has perhaps been the primary application to date, where the range of vehicle yaw angles tends to be quite limited. In fact, since yaw angles are typically developed as result of vehicle slip in cornering, or asymmetric set-up in the case of stock cars, they are limited to a few degrees. Further, since in both cases the vehicle centerline typically rotates with respect to the relative velocity vector (i.e. simulating vehicle slip in cornering), it seems clear that yawing the vehicle in the wind tunnel above a fixed (non-rotated) MGP is a valid simulation option. In the case of vehicles operating in strong crosswind conditions, for example commercial vehicles (heavy trucks) on interstate highways, the situation is more complex.