Progress in DES for wall-modelled LES of complex internal flows

Detached-Eddy Simulation (DES) was originally conceived for applications such as external aerodynamic flows with thin attached boundary layers and large-scale flow separation. In recent years a key modification to DES, known as IDDES, has been proposed that aims to extend its capabilities to include wall-modelled LES, which is particularly beneficial for cases typified by internal flows featuring thick boundary layers. IDDES of planar channel flow and the separating and re-attaching flow over periodic, two-dimensional hills is reported.Channel flow results indicate a satisfactory validation of the method, with a mild deviation believed to reflect an inherent numerics-sensitivity of IDDES. Very good agreement with benchmark data is achieved for the periodic 2D hills. In a systematic parameter study, the effects of turbulence modelling variation as well as strong grid and time step coarsening are investigated and discussed. The response of the method can generally be described as robust. The limits of time step coarsening are seen most clearly in the relationship between bulk flow and the driving pressure gradient. The importance of reporting this information is hence highlighted.A further investigation concerns the combination of IDDES with an all-y+ RANS wall treatment. For both test cases, grids without wall-normal refinement are employed as a particularly challenging test. In the planar channel, the Reynolds number dependence of grid resolution has been shown to be successfully eliminated. The results for the periodic hills are less satisfactory, which is attributed to the poor resolution of the hill-crest and early shear layer. A significant improvement over simulations without the all-y+ treatment however demonstrates the enhanced robustness achieved.