Manipulation of the Aerodynamic Behavior of the DrivAer Model with Fluidic Oscillators 2015-01-1540

The effect of an active flow control method is investigated on a 1:4 scale realistic vehicle model called “DrivAer” with notchback geometry. The wind tunnel experiments are conducted at a Reynolds number of Re=3.0·10⁶. Fluidic oscillators are applied at the c-pillars and at the upper rear edge of the window. The actuators are installed inside the hollow designed model emitting a high frequency sweeping jet. The spacing of the actuators, the mass flow rate, and the position of actuation are varied. The effect of the active flow control on the car is investigated with force and surface pressure measurements. The surface trace pattern is visualized with tufts for the active flow control cases and the baseline case. A tuft algorithm analyzes provides statistical data of the flow angles. Moreover, particle image velocimetry measurements are performed in the plane of symmetry for β=0° to capture the flow field at the rear end and the wake. The results indicate a significant pressure increase at the backlight and the upper trunk for increasing mass flow rates of the actuators. An increased pressure level of ΔC_P≈+0.35 is found compared to the non-actuated case. Furthermore, the aerodynamic forces show a decrease of the net drag of approximately ΔC_D,corr≈−3.5%. The downforce varies between ΔC_L,corr≈−25% and +38% depending on the actuation case. The tuft visualizations indicate a modification in the surface trace pattern at the rear end section of the notchback. The asymmetrical vortical structures at the backlight are typical on notchback rear ends and become smaller or vanish. The PIV measurements show a changed wake structure with a shifted location of the free stagnation point. Hence, the application of oscillating jets demonstrates a high potential to change the aerodynamic behavior of a realistic road vehicle design.