Rear-End Shape Influence on the Aerodynamic Properties of a Realistic Car Model: A RANS and Hybrid LES/RANS Study

The present work is concerned with the computational investigation of aerodynamic properties of the so-called ‘DrivAer’ car model representing a ‘generic realistic car configuration’ created by ‘merging’ the original geometries of two medium sized cars from the Audi A4 and the BMW 3 series, Heft et al. [7]. Three down-scaled (1:2.5) configurations differing in the rear-end shape—fastback, notchback and estate back geometries—investigated experimentally at the Institute of Aerodynamics and Fluid Mechanics Technical University in Munich are presently considered. The present numerical study focuses on the application of the ERM-capable (Elliptic-Relaxation Method) eddy-viscosity-based \(\zeta -f\) RANS model [6] describing turbulence within the Unsteady RANS (Reynolds-Averaged Navier-Stokes) and the so-called PANS (Partially-Averaged Navier-Stokes) computational frameworks. The latter approach representing a variable-resolution Hybrid RANS/LES (Large-Eddy Simulation) method is formulated and implemented into the CFD software package AVL-FIRE by Basara et al. [3]. The main objective of the present work is to check the models’ feasibility in computing the unsteady flow past the ‘DrivAer’ car configuration. The focus is on the varying structural properties of the flow arising from differently-shaped rear-ends and their impact on the surface pressure distribution and subsequently on the drag and lift force coefficients.