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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=3.2·106. 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.

The realistic car model DrivAer is investigated experimentally up to a Reynolds number of 2.8 million in the closed-loop wind tunnel at the "Technische Universitüt" Berlin. This new open-source design-hybrid of an "Audi A4™" and a "BMW 3 series™" possesses more representative car features as the well-known generic "Ahmed-Body." Therefore, the study of realistic flow structures is enabled. The main focus of the experimental investigations is the analysis of unsteady flow phenomena in the near wake of the model with a fastback configuration. An internal six component force balance and 63 pressure sensors measured simultaneously the forces and surface pressures with a sample rate of 5 kHz. Furthermore, the velocity field in the plane of symmetry is visualized through Particle Image Velocimetry. In the trailing edge region of the roof and the beginning of the rear window a local low pressure peak likely caused by a vortex is detected.