Drag Reduction of a Cube-Type Truck Configuration Through Boundary-Layer Control: Experiments and Prototype Road Tests

The paper presents results of an organized and extensive wind tunnel test-program, complemented by flow visualization and full-scale road tests, aimed at assessing the effectiveness of a boundary-layer control procedure for the drag reduction of a cube-van. Wind tunnel results, obtained using 1/6 scale model, at a subcritical Reynolds number of 10⁵, suggest that tripping of the boundary-layer using fences reduce the pressure drag coefficient. The entirely passive character of the procedure is quite attractive from the economic consideration as well as the ease of implementation. The road tests with a full-size cube-van substantiated the trends indicated by the fence data; although the actual drag reduction observed was lower (yet quite significant, 16.6%) than that predicted by the wind tunnel tests. This may be attribute to a wide variety of factors including the differences in the geometry and test conditions. Fuel consumption results also substantiated the drag reduction trend. It is concluded that fences can lead to a significant reduction in the drag and fuel consumption when applied to flat-faced trucks if positioned correctly. They represent an elegant, versatile, and economical approach to improve the truck performance.