Drag characteristics of a pickup truck according to the bed geometry

The bed of a pickup truck is the most important part for the aerodynamic performance. The drag characteristics of the pickup truck were examined experimentally according to the bed geometry which was the variation of the bed length and the bed height with three levels. The experiments were conducted at the low turbulence wind tunnel of the close type. The mean drag coefficients of the model were measured by a load cell varying in the yaw angle up to fifteen degrees. The flow field around the tailgate was visualized by the PIV (Particle Image Velocimetry) method and the surface flow on the upper part of the tailgate and sidewalls were visualized by the oil-paint method. The drag coefficients distribution was ascent or descent tendency according to the bed geometry, which showed that the bed length and the bed height were related closely to the flow characteristics. The bed height was the dominant factor for the short bed, while the reverse flow in wake was dominant for the long bed. The occurrence and the size of the reverse flow in wake are dependent upon the bed geometry. For the low drag pickup truck, the recirculating flow inside the bed and the reverse flow in wake should be considered at the same time.