LES Simulation to Predict the Cylinder Intake Phase Influence on the Airbox Efficiency 2010-01-0549
The fluid dynamic of fully turbulent flows is characterized by several length scales bounded between the flow field dimension (large scales) and the diffusive action of the molecular viscosity (small scale). The large scales of motion are responsible of the main momentum transport while the small scales of motion are responsible of the energy dissipation into heat.
In some cases the analysis of the large scales could be enough to explain the behaviour of the fluid dynamic system under investigation but, in other cases, the effect of all the turbulent scales have to be considered. A classic example of the latter working condition is the aerodynamic field where the efficiency is dictated by a fine equilibrium between mean flow conditions (driven by large turbulent scales) and laminar/turbulent boundary layer evolution (driven by small turbulent scales).
Today, race cars are good examples of complex aerodynamic systems where all the turbulent scales play a fundamental role on their aerodynamic efficiency. Moreover, in a race car also the engine performance can be strictly correlated to the aerodynamic efficiency because of the car body aerodynamic influence on the engine airbox fluid dynamic behavior.
This paper presents the application of Computational Fluid Dynamic (CFD) technique to analyze the fluid dynamic conditions inside a real geometry of an high performance car airbox. To solve the transient flow, the Large Eddy Simulation (LES) approach was adopted.
To reproduce realistic fluid dynamic conditions on the airbox inlet section, the car mock-up was connected to the airbox. The engine fluid dynamic influence on the airbox was taken into account by the application of 1D pressure profiles on the engine trumpet sections. Airbox performance, in terms of mean and
pressure and velocity evolutions, are compared to results previously obtained on the same computational domain without considering the cylinder intake phases.
All the simulations were performed by using FLUENT 6.3 CFD code. The
Wall Adaptive Local Eddy-Viscosity
model was adopted asclosure model for the governing equation set.