Investigation of the Turbulence Modeling Effects on the CFD Predictions of Passenger Vehicle Underhood Airflow 2018-01-0476

Computational Fluid Dynamics (CFD) tools play an important role in the early stages of vehicle aerothermal development. Arguably, the RANS (Reynolds Averaged Navier-Stokes) approaches are most widely used in industry due to their acceptable accuracy with affordable computational cost and faster turnaround time. In many automotive flows, RANS models cannot very accurately capture the absolute flow features or even the integral force coefficients. In spite of this, the RANS based CFD prediction results can conveniently be used to assess the magnitude and direction of a trend. However, even for such purposes, notable disagreements often exist between the flow features predicted by different RANS turbulence models. Whilst comparisons of different RANS models for various applications are abundant in literature, such evaluations on full-car models are limited, especially the evaluations of the cooling airflow inside the underhood compartment. In this study, four widely used RANS turbulence models, i.e., the realizable k − ε, AKN k − ε, SST k − ω, and V2F model will be assessed on a full-scale passenger vehicle. The vehicle model used in this study is a passenger car with four front-end configurations. In addition to typical external aerodynamic analysis, this study focuses on the underhood cooling airflow management, such as the radiator performance.