Investigation of the Flow Unsteadiness of Car Air-Box by Using LES

Today, high performance race car efficiency is based on a very fine equilibrium between aerodynamic efficiency, engine performance, and chassis behaviour. In particular, from the engine point of view, one way to increase the performance is to increase its volumetric efficiency. The aim of this paper is to present the application of the Large Eddy Simulation (LES) approach for the fluid dynamic analysis of a high performance race car airbox geometry. For a naturally aspired engine, the fluid dynamic optimisation of the airbox geometry means to optimise the energy conversion (from dynamic to static pressure) inside the airbox itself, therefore to increase the flow energy on the engine trumpet sections. The LES approach seems to be the best candidate to investigate such a flow since flow unsteadiness are expected to affect airbox efficiency in terms of pressure recovery. The airbox simulations were performed by using the commercial CFD code Fluent v6.3. The Wall Adaptive Local Eddy-Viscosity (WALE) Sub-Grid Scale (SGS) model was adopted together with a bounded second order central differencing scheme. The LES methodology here adopted was validated by previous works. In order to guarantee realistic fluid dynamic conditions on the airbox inlet section, a part of the car body was considered in the computational domain. Results obtained by LES simulations were analysed in terms of mean and rms evolutions of both pressure and velocity components. This study shows that, today, the LES technique is a very promising and proficient way to obtain detailed information about flow unsteadiness also on industrial cases.