INVESTIGATION OF CFD SETUP FOR AUTOMOTIVE APPLICATIONS
Renan Francisco Soares1; Francisco José de Souza1
1 Universidade Federal de Uberlândia
Resumo
An investigation of setup for CFD simulations of automotive applications is presented in this paper. As a test case, the DrivAer Fastback car model has been chosen. All simulations were performed in two dimensions. Thus, the profile in the symmetry plane DrivAer Fastback (with smooth underbody) car is adopted. Three of the most important factors are chosen for numerical simulation analysis, namely: (i) turbulence models, (ii) mesh base sizes and (iii) gradient methods. It shown that the drag prediction is very sensitive to mesh base size. As the surface base size is reduced, the simulation results for the different gradient methods tend to the same value. The conclusion is that the mesh base size has the major importance among the factors investigated. Regarding the turbulence model, SST k-ω turbulence model overpredicts the drag in comparison to Realizable k-ε under larger mesh base size. On the other hand, under smaller mesh base size, the SST k-ω turbulence model underpredicts the results with Realizable k-ε results. Such behaviour is very clear when using 2nd-order gradient methods. It leads to the conclusion that the first turbulence model is very sensitive to mesh base size, while the second shows smaller variations over different mesh base sizes. Regarding the gradient calculation method, they provide similar results under larger mesh base size. However, the 1st-order Green-Gauss has discrepant results from 2nd-order methods as the mesh base size decreases. In summary, the main contribution of this paper is the following best practices to set in CFD applications: (i) Realizable k-ε two-layer as turbulence model (robustness),(ii) smaller mesh base size over the car surface (better prediction of drag), and (iii) Green-Gauss or Hybrid LSQ in 2nd-order for gradient calculation method (numerical accuracy).
Palavras-chave: Aerodynamics; Automotive; DrivAer; CFD; RANS