Design and Evaluation of an Active Yaw and Turbulence Generation System to Produce Unsteady Flow in Automotive Wind Tunnels

This thesis summarizes the research, development, and testing of a novel unsteady yaw and turbulence generation system (TGS) for automotive wind tunnels that replicates on-road conditions using three combined subsystems. The focus of this thesis is primarily on one of the TGS subsystems, the unsteady yaw generation subsystem, which was made up of an airfoil-flap cascade. Tests were conducted in a 1/10th scale, 3/4 open-jet, wind tunnel and velocity data were obtained using two-component hotwire anemometry measurements that were spatially averaged. Yaw performance under different operating conditions, such as flap oscillation frequency and amplitude, was evaluated in terms of the phase-averaged flow behavior, the shape of the yaw angle distribution, and spectral distribution of velocity fluctuations. It is shown that the active yaw subsystem can generate bespoke yaw angle distributions. For example, the generated flows can mirror a variety of on-road flow conditions including the effect of traffic and vehicle wakes at highway speeds. The active system can also input a range of low frequency scales into the flow that are typical of those observed on-road. Preliminary tests indicate that the active yaw subsystem can operate in parallel with gust and turbulence subsystems to enhance flow spectrum designed to model on-road flows, however, future research is required to further optimize the TGS performance.