On the Performance of Various Reynolds Stress Models in Resolving Non-equilibrium Features of Turbulent In-cylinder Engine Flows

In highly transient turbulent flows, the energy cascade and related dissipation rate of energy are key factors which must be modeled precisely to obtain the accurate computational predictions. The flow in diesel engines specifically during compression stroke is quite transient, so most commonly used eddy viscosity based turbulence models fail to predict the transitional characteristics of these types of flow. This paper focuses on performance appraisal of three versions of Reynolds stress turbulence models in resolving non-equilibrium features and transitional characteristics of turbulent in-cylinder engine flows. Results indicate that although these turbulence models give the same prediction of averaged quantities of turbulent flows (i.e. mean flow kinetic energy), their results are totally different in calculating non-equilibrium features and the turbulent length scales. According to calculated results, incompressible Launder–Reece–Rodi and Naot second-moment closure models give unreal estimations of the turbulent integral length scale during compression stroke, while the modified Launder–Reece–Rodi model predictions have more similarity with physical trends.