Large eddy simulation analysis of engine steady intake flows using a mixed-time-scale subgrid-scale model

Large eddy simulation (LES) using a mixed-time-scale (MTS) subgrid-scale (SGS) model is applied to the intake flows in simplified internal combustion engine geometry. A modified colocated grid system is employed to obtain results as precise as possible and to perform calculations in a stable way with a central difference scheme for convective terms. The results are compared with corresponding experimental data and the Reynolds averaged Navier-Stokes (RANS) equation model results obtained using the low-Reynolds-number linear k-epsilon and cubic non-linear k-epsilon-A(2) turbulence models. LES results show the best agreement with experimental data in three computational cases, not only in the mean velocity profiles but also in the profiles of turbulent energy. These results suggest that LES with the MTS model is an effective method for accurately predicting the performance of a combustion engine. The cause of the insufficient prediction accuracy of the RANS models is also investigated. In addition, it is made clear that when the QUICK scheme is used in LES for the convective terms instead of the central difference scheme, the result obtained deteriorates owing to the numerical viscosity. The importance of the discretization method in practical LES is also confirmed.