Large eddy simulation for automotive aerodynamics with Alya

Abstract

The prodigious potential offered by the ever-growing computing infrastructure is fostering the use of large eddy simulation for automotive aerodynamics. This approach, which resolves the larger dynamically important eddies and models only the smaller ones, provides significant improvement over RANS when there are important separated regions or transient phenomena such as noise generation. In the search for high fidelity LES solution Alya has recently undergone a significant transformation departing from the use of the Variational Multiscale approach and implicit temporal discretization. Nowadays, Alya has switched to an explicit temporal discretization, without any stabilization other than the pressure stabilization introduced by the fractional step scheme. When using a energy conserving discretization for the convective term together with an explicit turbulent model, numerical stabilization of the convective term in the Navier Stokes equations is not needed. The Vreman turbulence model is used in this work. For the simulation of high Reynolds number turbulent flows, such as those encountered in automotive applications, the use of wall modeling is mandatory with current computational resources. Significant improvements in the implementation of wall modeling for finite element methods proposed recently are tested in this work for highly complex geometries. Comparison of the numerical results for both the Ahmed and DrivAer bodies against experimental results from the literature shows that Alya can provide very accurate results.