Assessment of hybrid RANS-LES methods for accurate automotive aerodynamic simulations

The introduction of the Harmonized Light Vehicles Test Procedure causes a significant challenge for the automotive industry, as it increases the importance of efficient aerodynamics and demands how variations of optional extras affect the car’s fuel consumption and emissions. This may lead to a huge number of combinations of optional extras that may need to be aerodynamically analyzed and possibly optimized, being to resource-consuming to be done with wind tunnel testing merely. Reynolds Average Navier-Stoles (RANS) coupled with Large Eddy Simulations (LES) have shown potential for accurate simulation for automotive applications for reasonable computational cost. In this paper, three hybrid RANS-LES models are investigated on the DrivAer notchback and fastback car bodies and compared to wind tunnel measurements. Several yaw angles are investigated to see the model’s ability to capture small and large changes of the flow field. It is seen that the models generally are in good agreement with the measurement, but only one model is able to capture the behavior seen in the measurements consistently. This is connected to the complex flow over the rear window, which is important to capture for accurate force predictions. •Three hybrid RANS-LES models are compared to wind tunnel measurements for two DrivAer car body configurations.•The turbulence models RANS shielding and transition to LES region properties are essential for achieving consistent accuracy.•The SBES model is the only model to capture the complex flow over the rear window of the notchback car configuration.•The DDES and IDDES models suffer from insufficient shielding of the RANS region and premature switch to WMLES, respectively.