Localized Dynamic Subgrid-scale Model Research Articles

Lagrangian dynamic SGS model for stochastic coherent adaptive large eddy simulation

Stochastic coherent adaptive large eddy simulation (SCALES) is an extension of large eddy simulation that uses a wavelet filter-based dynamic grid adaptation strategy to solve for the most energetic coherent structures in a turbulent flow field, while modeling the effect of the less energetic ones. A localized dynamic subgrid scale model is needed to fully exploit the ability of the method to track coherent structures. In this paper, new local Lagrangian models based on a modified Germano dynamic procedure, redefined in terms of wavelet thresholding filters, are proposed. These models extend the original path-line formulation of Meneveau et al. [J. Fluid Mech. 319 (1996)] in two ways: as Lagrangian path-line diffusive and Lagrangian path-tube averaging procedures. The proposed models are tested for freely decaying homogeneous turbulence with initial Re λ = 72. It is shown that the SCALES results, obtained with less than 0.4% of the total non-adaptive nodes required for a DNS with the same wavelet solver, closely match reference DNS data. In contrast to classical LES, this agreement holds not only for large scale global statistical quantities, but also for energy and, more importantly, enstrophy spectra up to the dissipative wavenumber range.

An Investigation of the Localized Dynamic Mixed SGS Model and its Application to Turbulent Channel Flow.

The drawbacks of the dynamic sub-grid scale eddy viscosity model proposed by Germano et al. in 1991 are that homogeneous direction of turbulence is required to eliminate numerical instability due to negative eddy viscosity and that the model is unable to predict sub-grid scale turbulent energy backscattering from sub-grid scale to grid scale. In the present study, the localized dynamic sub-grid scale model proposed by Meneveau et al. in 1994 was utilized with the mixed sub-grid scale model proposed by Vreman et al. in 1994 to eliminate these shortcomings. A newly developed eddy viscosity type sub-grid scale model was used instead of Smagorinsky's model which does not require the local equilibrium state of SGS energy. The proposed model was tested by simulating turbulent channel flow at Re=180 normalized by channel-half width and friction velocity. The results showed good agreement with direct numerical simulation data obtained by Kim et al. Relationships between the turbulent coherent structures and the Grid scale turbulent energy dissipation by the SGS model were also investigated. Some advantages of using the scale similarity model to simulate turbulent coherent structures were pointed out.