A note on spectral energy transfer for multiscale eddy viscosity models in large-eddy simulations

Abstract

The multiscale approach to large-eddy simulation has shown potential to yield improved results over conventional eddy viscosity implementations with a relatively small increase in computational expense. Several variants of the modeled subgrid stress have been proposed, but no conclusions have been drawn regarding which formulations are the most accurate or physically appropriate. This Brief Communication presents a case for choosing a particular form for the subgrid stress tensor, based on relatively simple energy transfer concepts and inertial subrange scaling laws. It is proposed that two requirements should be satisfied. First, that the eddy viscosity depend only on the portion of the resolved energy spectrum near the filter cutoff, and second, that the modeled stress tensor permit energy transfer from the low wave-number modes to the subgrid scales. The result is a “small-large” multiscale variant for the subgrid stress. Results are presented for isotropic decaying turbulence and a transitioning planar jet case.