Using Multi-Fidelity Turbulence Modelling Approaches to Analyse DrivAer External Aerodynamics 2023-01-0016
Increasing fuel and electricity prices create high pressure to develop efficient external aerodynamics of road cars. At the same time, development cycles are getting shorter to meet changing customer preferences while physical testing capacities remain limited, creating a pressing need for fast and accurate turbulence models to predict aerodynamic performance.
This paper introduces and discusses different turbulence modelling approaches beyond the well-known and established models used today in the industry. The RANS Lag Elliptic Blending (Lag EB) k − ϵ model, which enables highly accurate steady-state RANS, was chosen as the baseline approach. As a medium fidelity approach Scale-Resolving Hybrid (SRH) model was utilized, which modifies a RANS base model to produce a smooth transition between URANS and LES behavior. The Wall-Modelled LES (WMLES) method was chosen for high fidelity simulations.
To validate the presented models, a detailed set of experimental data from the 3rd Automotive CFD Prediction Workshop was utilized. Simulations were run on the grid provided for the workshop; in addition, a reviewed volume mesh was utilized. The numerical results of the aforementioned turbulence models are discussed against experimental results of the DrivAer baseline case and its variant with front wheel deflectors. In addition to force coefficients, flow field visualizations are available, providing additional insights.
The simulations show an excellent agreement for the Lag EB runs with the experimental data for the baseline model in terms of drag prediction. Scale-resolving simulations require appropriate numerical set-up for accurate drag prediction. The impact of the front wheel deflector on drag is consistently predicted by all three methods.
