SAE International Experimental Comparison of the Aerodynamic Behavior of Fastback and Notchback DrivAer Models 2014-01-0613

The experimental investigation was conducted with a 25%-scaled realistic car model called "DrivAer" mounted in a wind tunnel. This model includes geometric elements of a BMW 3 series and an Audi A4, accommodating modular, rear-end geometries so that it represents a generalized modern production car. The measurements were done with two different DrivAer rear end configurations (fastback and notchback) at varying side-wind conditions and a Reynolds number of up to Re=3.2\u00b710 2x. An array of more than 300 pressure ports distributed over the entire rear section measured the temporal pressure distribution. Additionally, extensive flow visualizations were conducted. The combination of flow visualization, and spatially and temporally resolved surface pressure measurements enables a deep insight into the flow field characteristics and underlying mechanisms. Moreover, static pressure fluctuations indicate regions with a high turbulence level due to flow separation and interaction between different vortical structures. A directional decomposition of the pressure coefficient is demonstrated and acts generally normal to the surface of the vehicle, in the drag and lift direction.