Abstract
Predicting the behavior of turbulent flows using large-eddy simulation requires a modeling of the subgrid-scale stress tensor. This tensor can be approximated using mixed models, which combine the dissipative nature of functional models with the capability of structural models to approximate out-of-equilibrium effects. We propose a mathematical basis to mix (functional) eddy-viscosity models with the (structural) Bardina model. By taking an anisotropic minimum-dissipation (AMD) model for the eddy viscosity, we obtain the (single-layer) AMD–Bardina model. In order to also obtain a physics-conforming model for wall-bounded flows, we further develop this mixed model into a two-layer approach: the near-wall region is parameterized with the AMD–Bardina model, whereas the outer region is computed with the Bardina model. The single-layer and two-layer AMD–Bardina models are tested in turbulent channel flows at various Reynolds numbers, and improved predictions are obtained when the mixed models are applied in comparison to the computations with the AMD and Bardina models alone. The results obtained with the two-layer AMD–Bardina model are particularly remarkable: both first- and second-order statistics are extremely well predicted and even the inflection of the mean velocity in the channel center is captured. Hence, a very promising model is obtained for large-eddy simulations of wall-bounded turbulent flows at moderate and high Reynolds numbers.
Highlights
Predicting the behavior of turbulent flows is still one of the major challenges in the field of computational fluid dynamics
In order to obtain a physics-conforming model for wall-bounded flows, we further develop this mixed model into a two-layer approach: the near-wall region is parameterized with the anisotropic minimum-dissipation (AMD)–Bardina model, whereas the outer region is computed with the Bardina model
In order to take the various flow phenomena present in nearwall turbulence into account, we propose the utilization of a twolayer approach for the AMD–Bardina mixed model: the AMD–Bardina model is utilized in the near-wall domain, i.e., in the inner layer, since this model introduces dissipation through the eddy-viscosity model part while accounting for the interaction between turbulent structures as well as for backscatter of energy through the scale-similarity part
Summary
Predicting the behavior of turbulent flows is still one of the major challenges in the field of computational fluid dynamics. Salvetti and Banerjee improved the dynamic mixed model of Zang et al., dynamically computing the model parameters of the eddy-viscosity and the scale-similar parts Their so-called dynamic two-parameter model was tested for the flow between a no-slip wall and a free-slip surface, and the results were compared to the predictions obtained with the application of the dynamic Smagorinsky model of Germano et al., the dynamic mixed model of Zang et al., and DNS data from Lam and Banerjee.. The subgrid-scale stress tensor is approximated by the Bardina model only, as relatively little energy is dissipated in this region This new two-layered mixed model is here called the twolayer AMD–Bardina model, whereas the model that does not consider the division of domains is called the single-layer AMD–Bardina model. V, the current work is summarized, and further directions of study are suggested
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