On the Drag Reduction of Trucks through the Application of Fences and Momentum Injection

The paper studies effectiveness of two fundamentally different concepts of boundary-layer control for reduction of drag of bluff bodies: Moving Surface Boundary-layer Control (MSBC) involving momentum injection delaying separation; and tripping of the boundary-layer, using judiciously located fences, to interrupt pressure recovery. Wind tunnel tests, with two-dimensional models of rectangular prisms and 1/12 scale model of a typical tractor-trailer truck configuration, show both the approaches to be quite effective promising a significant reduction in the aerodynamic resistance. A flow visualization study, conducted in a closed circuit water tunnel using slit lighting and polyvinylchloride tracer particles, complements the wind tunnel tests. It shows, rather dramatically, effectiveness of the boundary-layer control procedures.