Numerical Analysis using Fast RANS simulations and Comparison with Experimental Measurements for Closed and Open Grille Realistic Car Models 2019-01-0655
Over the past few years, the DrivAer car geometry has driven development of simulation methodology for vehicle aerodynamics. Due to the realistic geometry of the DrivAer car model the results obtained from simulations can be easily extended to the aerodynamic design process of production vehicles. This paper details a comprehensive CFD study of all three variants of the DrivAer car geometries: Fastback, Notchback and Estate configurations. The most realistic geometry was chosen for each of the variants; with detailed underbody, wheels and mirrors. In addition to the closed-grille standard DrivAer models, the open–grille variant has also been simulated. Simulations are performed both with and without ground simulation. Mesh generation was performed without surface alterations (e.g. wrapping) using a novel Binary-Tree automatic unstructured mesher. All simulations were performed using RANS turbulence model. A consistent modeling methodology was developed that was rigorously applied to all variants of the DrivAer model and the simulations are shown to have consistently good agreement with experimental measurements. This demonstrates the potential of using such a methodology for several different types of vehicles during the design process.
In addition to presenting the detailed methodology and the results, a thorough review was conducted and comparisons are made with the existing body of literature on the DrivAer model: including both RANS and RANS-LES hybrid turbulence models. The accuracy of the RANS simulation performed for the present work was shown to be comparable with more complex turbulence models and expected to be at a fraction of the computational cost. In addition to comparing integrated quantities such as the drag coefficient for each of the variants, further detailed spatial comparison of simulation results with experimental measurements are also presented; including a detailed look at the highly sensitive rear window wake region of the Fastback, Notchback and Estate DrivAer models.