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A wind-tunnel test was conducted for an unswept wing with a half-span Fowler flap. Surface pressures, flow visualization, and wake surveys were obtained for two flap riggings representative of landing configurations. The primary influence of the half-span flap is to create spanwise pressure gradients on the main element and flap. Pressure distributions near the flap tip indicate the presence of two distinct suction peaks on the upper surface. Flow visualization using smoke verifies the existence of two co-rotating vortices near the flap tip that merge before reaching the trailing edge. Seven-hole-probe wake surveys yield values for both profile and induced drag.

The effectiveness of an aerodynamic boattail on a tractor/trailer road vehicle was measured in the NASA Ames Research Center 80- by 120- Foot Wind Tunnel. Results are examined for the tractor/trailer with and without the drag reduction device. Pressure measurements and flow visualization show that the aerodynamic boattail traps a vortex or eddy in the corner formed between the device and the rear corner of the trailer. This recirculating flow turns the flow inward as it separates from the edges of the base of the trailer. This modified flow behavior increases the pressure acting over the base area of the truck, thereby reducing the net aerodynamic drag of the vehicle. Drag measurements and pressure distributions in the region of the boattail device are presented for selected configurations. The optimum configuration reduces the overall drag of the tractor/trailer combination by about 10 % at a zero yaw angle.