Investigation of the effect of an anisotropy-resolving subgrid-scale model on budgets of the Reynolds stresses

In large eddy simulation (LES), the prediction accuracy of the mean velocity is closely related to that of the ensemble-averaged Reynolds (Re) shear stress that consists of the resolved grid-scale (GS) and unresolved subgrid-scale (SGS) parts. It is generally understood that an SGS model plays a role of compensating the lack of the GS part that is originally cut off through a filtering process. Besides this basic role, however, it is expected that an SGS model directly influences instantaneous vortex motions through the momentum equations, leading to a change of the distribution of the averaged GS stresses because the instantaneous fluctuation of the SGS stress is closely related to that of the strain rate in the budget of the GS part. In the present study, to discuss this problem in more detail, an anisotropy-resolving SGS model was carefully investigated. We focused mainly on the contribution of the SGS stress to the prediction accuracy of the ensemble-averaged resolved GS stress through its budget.