Experimental Study of Baseline Flow Characteristics for the Realistic Car Model DrivAer 2013-01-1251

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. This vortex may sustain the flow attachment downstream and hence, improves the pressure recovery. Although instantaneous flow field snapshots illustrate large-scale structures and the meandering of a free stagnation point in the model's wake, no dominant frequencies are found from spectral analysis of time-resolved pressure and force measurements.