A Sub-grid Scale Model with Non-traditional Eddy-Viscosity Coefficient

摘要

In this paper, a zero-equation sub-grid scale (SGS) model with a variable C_μ is developed for large-eddy simulation. The model coefficient C_μ is determined based on the resolved shear and vorticity parameters accompanied by the hybrid time scale (based on dynamic and Kolmogorov time scales). The proposed model accounts for the SGS kinetic energy by the relation k_(sgs) = C_μ~(2/3) (ΔS)~2 , where S is the invariant of resolved strain-rate tensor and Δ is the grid-filter width. The new model is sensitive to shear and vorticity parameters, making it suitable for flows that are far from equilibrium. Since C_μ acts as a natural damping function, there is no need for such a function in the proposed model. The model requires only a single filter making it more robust to use in majority of fluid flow problems. In addition, it requires no ad-hoc approach for achieving the numerical stability. To demonstrate its predictive capabilities, computations are performed for fully developed channel flows and a diffuser flow which are compared with the direct numerical simulation (DNS) and experimental data. Excellent agreement is obtained. Comparisons indicate that the new model offers some advantages over the dynamic Smagorinsky model (DSM).