Aerodynamic Drag of Bluff Body Shapes Characteristic of Hatch-Back Cars

The flow around a bluff body with a slanted rear surface is influenced very dramatically by changing the angle of the rear surface slant and at some slant angles an excessively high drag is generated. To learn more about this critical behavior a series of detailed experiments was conducted on a vehicle-like bluff body, investigating the effect of ground proximity, Reynolds number, free-stream turbulence and of rounding of the upper edge of the slanted surface. The results of these experiments showed that although these various factors could change the critical slant angle and the size of the drag overshoot, the basic critical behavior was always present.