Advancements in dynamic subgrid-scale modeling for large-eddy simulations (LES) of turbulent flows*

In LES methodology, one of the drawbacks of eddy-viscosity-based subgrid-scale(SGS) models is the misalignment between residual stresses and large-scale strain rate tensor. Further, since small-scale turbulence is generated from 3-D vortex stretching, it is desirable to include large-scale rotation rate tensor in phenomenological SGS models. Early attempts at developing higher-fidelity SGS models led to tuned model coefficients and/or under-dissipative models (Meneveau and Katz, Annu. Rev. Fluid Mech. 2000).

We propose novel dynamic formulations of the tensor-coefficient Smagorinsky model (Moin, Springer 1993), and a non-linear model characterized by the full velocity-gradient tensor (Lund and Novikov, Res. Briefs, CTR 1992) using the Germano identity while preserving the rotational invariance of the Navier Stokes equations. We also validate these models in decaying and forced Homogeneous Isotropic Turbulence at Re_λ = 70 & 410 respectively, followed by wall-modeled LES of channel flow at Re_τ = 4200. Results from simulations of complex-separated flows such as the Boeing Speed Bump using these models will also be reported and compared to that of other models.