Drag Reduction on Blunt-Based Vehicles Using Forebody Surface Roughness

The article of record as published may be found at http://dx.doi.org/10.2514/2.3849Results of wind-tunnel tests that demonstrate a novel drag reduction technique for blunt-based vehicles are presented. For these tests, the forebody roughness of a blunt-based model was modified using micromachined surface overlays. As forebody roughness increases, the boundary layer at the model aft thickens and reduces the shearing effect of external flow on the separated flow behind the base region, resulting in reduced base drag. For vehicle configurations with large base drag, existing data predict that a small increment in forebody friction drag will result in a relatively large decrease in base drag. If the added increment in forebody skin drag is optimized with respect to base drag, reducing the total drag of the configuration is possible. The wind-tunnel tests results conclusively demonstrate the existence of a forebody drag–base drag optimal point. The data demonstrate that the base drag coefficient corresponding to the drag minimum lies between 0.225 and 0.275, referenced to the base area. Most important, the data show a drag reduction of approximately 15% when the drag optimum is reached