Forcing air through strategically placed slits on a tractor trailer results in a major boost in fuel economy, new road tests of diesel-fueled trucks show.
Typically, a boxy trailer moving at highway speeds generates a turbulent wake that exerts a retarding force, or drag. But on a trailer modified to have slits and rounded contours at its back edges, sheets of air pumped by fans rearward through those slits hug the curved contours and entrain air rushing over the trailer into an orderly current. That effect sharply cuts drag.
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