Large-eddy simulation of stratified turbulence. Part I: A vortex-based subgrid-scale model

Abstract

The stretched-vortex subgrid-scale (SGS) model is extended to enable large-eddy simulation of buoyancystratified turbulence. Both stable and unstable stratifications are considered. The extended model retains the anisotropic form of the original stretched-vortex model, but the SGS kinetic energy and the characteristic SGS eddy size are modified by buoyancy subject to two constraints: first, the SGS kinetic energy dynamics is determined by stationary and homogeneous conditions, and second, the SGS eddy size obeys a scaling analogous to the Monin-Obukhov similarity theory. The SGS model construction, comprising an ensemble of subgrid stretched-vortical structures, naturally limits vertical mix..