Comparison of the Different Hybrid RANS/LES Methods for Unsteady Numerical Simulation of the Flow around an Automotive Generic Model

Abstract:

Unsteady numerical simulations were carried out using different RANS/LES hybrid methods for the outflow field of the MIRA generic model. The applicability of RANS/LES hybrid methods （DDES， IDDES， SBES， SDES） and DDES based on different RANS models （RKE， SA， SST k-ω， GEKO k-ω） in calculating the automotive outflow field was explored through detailed comparative analyses with the results of the wind tunnel experimental measurements of aerodynamic forces and pressures. The study shows that the results of different hybrid methods are all on the high side in predicting aerodynamic coefficients， with the DDES-GEKO model having the smallest relative error. For surface pressure coefficients， the predictive results of different hybrid methods for the vertical center line are in good agreement with the experimental values， among which the SBES-GEKO model performs better. The embedded RANS models in the DDES show significant differences in predicting pressure on the rear windshield， with the SA model being better. The pressure predictions for the underbody are deviated by different hybrid methods， with the pressure predictions for the front part being smaller than experimental values， while the SBES-GEKO model gives better results for the rear part. Additionally， the SBES-GEKO model is able to identify the unsteady flow structures in the wake region well.

Key words:MIRA generic model;unsteady numerical calculation;hybrid Reynolds-averaged Navier-Stokes/Large Eddy Simulation(RANS/LES) method