On the Applications of Low-Reynolds Cubic k-εTurbulence Models in 3D Simulations of ICE Intake Flows

The evaluation of the steady-flow discharge coefficient of ICE port assemble is known to be very sensitive to the capability of the turbulence sub-models in capturing the boundary layer dynamics. Despite the fact that the intrinsically unsteady phenomena related to flow separation claim for LES approach, the present paper aims to demonstrate that RANS simulation can provide reliable design-oriented results by using low-Reynolds cubic k-ε turbulence models.

Different engine intake port assemblies and pressure drops have been simulated by using the CFD STAR-CD code and numerical results have been compared versus experiments in terms of both global parameters, i.e. the discharge coefficient, and local parameters, by means of static pressure measurements along the intake port just upstream of the valve seat. Computations have been performed by comparing two turbulence models: Low-Reynolds cubic k-ε and High-Reynolds cubic k-ε.

The analysis leaded to remarkable assessments in the definition of a correct and reliable methodology for the evaluation of engine port breathing capabilities. Comparison between numerical results and experiments showed that the low-Reynolds cubic k-ε model is unavoidable to correctly capture the influence of port feature variations on engine permeability. In particular, the deficiencies demonstrated by High-Reynolds cubic k-ε turbulence model in resolving the influence of near-wall shear and adverse pressure gradient effect on boundary layer dynamics are completely overcome by the use of the Low-Reynolds formulation.