Towards a Standardized Assessment of Automotive Aerodynamic CFD Prediction Capability - AutoCFD 2: Ford DrivAer Test Case Summary 2022-01-0886

The 2^nd Automotive CFD Prediction workshop (AutoCFD2) was organized to improve the state-of-the-art in automotive aerodynamic prediction. It is the mission of the workshop organizing committee to drive the development and validation of enhanced CFD methods by establishing publicly available standard test cases for which high quality on- and off-body wind tunnel test data is available.

This paper reports on the AutoCFD2 workshop for the Ford DrivAer test case. Since its introduction, the DrivAer quickly became the quasi-standard for CFD method development and correlation. The Ford DrivAer has been chosen due to the proven, high-quality experimental data available, which includes integral aerodynamic forces, 209 surface pressures, 11 velocity profiles and 4 flow field planes. For the workshop, the notchback version of the DrivAer in a closed cooling, static floor test condition has been selected. For a better comparability of CFD results, two carefully designed control meshes were provided. Both meshes share identical distributions in the flow field volume but differ in near wall spacing to allow for wall-modelled and wall-resolved solutions.

The 65 results, which were submitted by 22 participants, revealed a very significant variability of the aerodynamic force predictions even when using the same turbulence model on the control grids. While individual simulations using scale-resolving hybrid turbulence models correlated very well to the experimental flow field data, other analyses using almost identical simulation approaches resulted in very different predictions. The comparison of transient versus steady state analysis confirmed that transient simulations deliver more accurate flow field predictions. A significant impact of the near wall mesh resolution could not be confirmed by the results submitted for the DrivAer test case.