Scale-Resolving Simulations Combined with the Immersed Boundary Method for Predicting Car Aerodynamics

This paper presents calculations of external car aerodynamics by using the Partial-Averaged Navier-Stokes (PANS) variable resolution model in conjunction with the finite volume (FV) immersed-boundary method. The work presented here is the continuation of the study reported in Basara et al. [1]. In that work, it was shown that the same accuracy of predicted aerodynamic forces can be achieved by using Reynolds-Averaged Navier-Stokes (RANS) k-ζ-f model on both types of meshes, the standard body-fitted (BF), and on the immersed boundary (IB) mesh. Due to all well-known shortcomings of the steady state approach, in this work we deal with the Partially Averaged Navier-Stokes (PANS), which belongs to the hybrid RANS-LES (scale resolving / high fidelity) methods. This approach was developed to resolve a part of the turbulence spectrum adjusting seamlessly from RANS to DNS (Direct Numerical Simulation). The PANS model variant used for the present calculations is based on the near-wall RANS k-ζ-f model. The numerical implementation of the wall treatment on the IB meshes is the same as in the previously reported RANS calculations. The significant speed-up of the PANS calculations was achieved by using the fractional step method. Comparisons of the PANS results on both types of meshes with the experimental data for the well-known DrivAer notchback model (Hupertz et al. [2]) demonstrate the predictive capability of PANS in the IB framework.