Eddy-resolving Simulations of the Notchback ‘DrivAer’ Model: Influence of Underbody Geometry and Wheels Rotation on Aerodynamic Behaviour 2016-01-1602

The present work deals with a computational study of a ‘DrivAer’ car model, the rear-end shape of which corresponds to the Notchback configuration (Heft et al. [1] and Heft [2]). The study investigates the effects of the underbody geometry and wheel rotation on the aerodynamic performance. The configurations with detailed and smooth underbody as well as with stationary and rotating wheels are considered. The computational model applied relies on a VLES (Very Large Eddy Simulation) formulation, Chang et al. [3]. The residual turbulence related to the VLES framework is presently modelled by a RANS-based (Reynolds-Averaged Navier-Stokes), four-equation (D(k,ɛ,ζ, f)/Dt) near-wall eddy-viscosity model, Hanjalic et al. [4]. In addition to the equations governing the kinetic energy of turbulence (k_us) and its dissipation rate (ɛ_us), it solves a transport equation for the quantity , representing a key parameter, as it models the velocity scale in the expression for the corresponding turbulence viscosity. In addition to VLES, all considered flows are simulated within both RANS and Unsteady RANS (URANS) frameworks using the same background model formulation representing the constituent of the VLES method. Whereas the “k-ɛ-ζ-f” model describes fully-modelled turbulence within the RANS/URANS method, it relates to the unresolved sub-scale turbulence within the VLES framework (the relevant quantities are denoted by the subscript ‘us’). Unlike the RANS/URANS method, the VLES method is capable of capturing the spectral dynamics of turbulence to an extent complying with the underlying grid resolution. Accordingly, the superiority of the VLES method is especially visible at the computed evolution of the aerodynamic coefficients, agreeing reasonably well with the experimental database.