Active Crosswind Generation and Its Effect on the Unsteady Aerodynamic Vehicle Properties Determined in an Open Jet Wind Tunnel

In this article the unsteady aerodynamic properties of a 25% scale DrivAer notchback model as well as the influence of the wind tunnel environment on the resulting unsteady aerodynamic forces and moments under crosswind excitation are investigated using experimental and corresponding numerical methods. Research Institute of Automotive Engineering and Vehicle Engines Stuttgart (FKFS) swing® (side wind generator) is used to reproduce the essential properties of natural stochastic crosswind in the open jet test section of the Institute for Internal Combustion Engines and Automotive Engineering (IVK) model scale wind tunnel (MWK). The results show that the test environment of an open jet wind tunnel alters the amplitudes of side force and yaw moment under crosswind excitation when compared to an ideal environment neglecting wind tunnel interference effects. The presented approach for the quantification of the unsteady behavior of the flow field provides a basic understanding of the phenomena occurring under the dynamic deflection of a wind tunnel jet. It is shown that the wind tunnel jet has a dynamic behavior that is superimposed on the aerodynamic response of the vehicle. The investigation of different model scales gives information about the interaction of the dynamic jet behavior with the vehicle response as well as the magnitude of the expected influence. For the first time, a validated simulation model of the unsteady aerodynamic vehicle properties of the realistic DrivAer model as well as of the model scale wind tunnel is introduced. The presented simulation environment without interference effects allows the quantification of the unsteady aerodynamic response of a vehicle without external influences.