Spectral eddy viscosity of stratified turbulence

Abstract

The analysis of the spectral eddy viscosity is a handy tool to analyze the performance of LES methods. It reflects the cumulated effect of numerical discretization and turbulence subgrid-scale model on the spectral energy transfer. We compute this quantity by filtering and truncating data from direct numerical simulations of neutrally and stably stratified homogeneous turbulence. The results are used for testing of implicit and explicit LES methods. We find indications that for stably stratified turbulence it is necessary to use different subgrid-scale models for the horizontal and vertical velocity components.