Experimental and Numerical Investigations on Time-Resolved Flow Field Data of a Full-Scale Open-Jet Automotive Wind Tunnel

One main goal of the automotive industry is to reduce the aerodynamic drag of passenger vehicles. Therefore, a deeper understanding of the flow field is necessary. Time-resolved data of the flow field is required to get an insight into the complex unsteady flow phenomena around passenger vehicles. This data helps to understand the temporal development of wake structures and enables the analysis of the formation of vortical structures. Numerical simulations are an efficient method to analyze the time-resolved data of the unsteady flow field. The analysis of the steady and unsteady numerical data is only relevant for aerodynamic developments in the wind tunnel, if the predicted temporal evolving structures of a passenger vehicle's simulated flow field correspond to the structures of the flow field in the wind tunnel. In this study, time-resolved measurements of the empty wind tunnel and a notchback passenger vehicle in the wind tunnel are conducted. The temporal structures of the vehicle's wake are investigated with a hot-wire anemometer. These measurements help to understand the occurring unsteady flow phenomena at the vehicle in the wind tunnel. Furthermore, the measured data is used as a reference for the comparison of the time-resolved numerical data with the experimental data. For the numerical data, an unsteady Spalart-Allmaras Delayed Detached Eddy Simulation in OpenFOAM® is used and compared to measurements in an automotive wind tunnel. This comparison shows differences in the unsteady datasets. Therefore, a novel approach for the numerical simulation of wind tunnel tests is presented here. A temporal evolving boundary condition ensures an improved correlation between the numerical data and the experimental wind tunnel data. With this optimized numerical setup, fundamental improvements are achieved. Additionally, the findings of numerical time-resolved analysis methods are gaining in relevance for the aerodynamic development.