Using LES for Predicting High Performance Car Airbox Flow

Aerodynamics have played a primary role in high-performance cars since the late 1960s, when introduction of the first inverted wings appeared in some formulas. Race car aerodynamic optimization is one of the most important reasons behind the car performance. Moreover, for a high-performance car using naturally aspired engine, car aerodynamics have a strong influence also on engine performance by its influence on the engine airbox. To improve engine performance, a detailed fluid dynamic analysis of the car/airbox interaction is highly recommended. To design an airbox geometry, a wide range of aspects must be considered because its geometry influences both car chassis design and whole car aerodynamic efficiency. To study the unsteady fluid dynamic phenomena inside an airbox, numerical approach could be considered as the best way to reach a complete integration between chassis, car aerodynamic design, and airbox design. This paper presents the application of Large Eddy Simulation (LES) approach to the study of the unsteady flow conditions inside a real geometry of a high-performance car airbox. LES is a promising technique to yield a CFD tool able to predict flow unsteadiness since LES numerical modeling concerns only a small part of the energy spectrum while the large-scale motion is directly resolved. The FLUENT 6.3 code has been used and the Wall Adaptive Local Eddy-Viscosity (WALE) sgs model has been adopted. A Bounded Central Differencing (BCD) second-order scheme has been adopted and a discussion of the kinetic energy conservation attitude of such a scheme performed. Results obtained by LES simulations have been analyzed in terms of mean evolution and rms fluctuations of both pressure and velocity components.