Evaluation of various rans turbulence models for predicting the drag on an ahmed body

The focus of this paper is on simulation of flow past an Ahmed body with a rear slant angle of 25°. Reynolds-Averaged Navier-Stokes (RANS) equations are solved in conjunction with various turbulence models using the finite-volume method. The turbulence models employed are the k-ε standard and realizable models, k-ω shear stress transport (SST) model, Spalart-Allmaras (SA) model and the wall-distance free Wray-Agarwal model (WA2018). Each turbulence model is run with both a coupled and a simple pressure-velocity algorithm. A pressure-based solver in the ANSYS Fluent CFD software package is used for the computations. Computational results using various turbulence models are compared to assess their ability to predict accurately the drag coefficient of the Ahmed body and in the computational time required. Simulation conditions are obtained from the experimental wind tunnel data for the Ahmed body model geometry. Computational results show that k-ε realizable, k-ω SST and WA models yield values closer to the experimental data with WA model requiring less simulation time per iteration than the other two models. The variation in the computational results can be primarily attributed to the differences in the wall-boundary layer treatment among various turbulence models.