Abstract
The general framework of large-eddy simulations (LES) is presented first, with Smagorinsky's model. Afterwards, Kraichnan's spectral eddy-viscosity is introduced and it is shown how it can be handled for LES purposes in isotropic turbulence. The spectral eddy viscosity is generalized to a spectral eddy diffusivity. The nonlocal interaction theory is used to discuss the backscatter issue, and a generalization of spectral eddy coefficients is presented. This so-called spectral-dynamic model allows the representation of non-developed turbulence in the subgrid scales. Utilization of these spectral models in physical space is envisaged in terms of, respectively, the structure function and hyperviscosity models. Two applications of these models to shear flows are considered, namely the plane mixing layer and channel flow, with statistical results and information on the topology of coherent vortices and structures presented.
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