Some Developments in DES Modeling for Engine Flow Simulation 2015-24-2414

Scale-resolving turbulence modeling for engine flow simulation has constantly increased its popularity in the last decade. In contrast to classical RANS modeling, LES-like approaches are able to resolve a larger number of unsteady flow features. In principle, this capability allows to accurately predict some of the key parameters involved in the development and optimization of modern engines such as cycle-to-cycle variations in a DI engine. However, since multiple simulated engine cycles are required to extract reliable flow statistics, the spatial and temporal resolution requirements of pure LES still represent a severe limit for its wider application on realistic engine geometries. In this context, Hybrid URANS-LES methodologies can therefore become a potentially attractive option. In fact, their task is to preserve the turbulence scale-resolving in the flow core regions but at a significantly lower computational cost compared to standard LES. In this paper, we present our achievements in the development of an original hybrid simulation method which relies on the Detached Eddy Simulation (DES) concept applied to a reformulated two-equation turbulence model. The resulting method has been implemented in the open-source CFD toolbox OpenFOAM® and initially assessed against a standard freely decaying turbulent flow case with considerations on the numerical schemes optimal choice. Subsequently, the proposed model has been applied on geometries presenting different levels of complexity, mimicking some of the typical flow conditions encountered at an engine intake port. The current numerical predictions have been compared with the available experimental data as well as with previous computational studies performed on the same flow configurations.