Subgrid-Scale Model and Resolution Influences in Large Eddy Simulations of Channel Flow

Abstract

Subgrid-scale (SGS) modeling and resolution are two important issues that can affect the quality of large eddy simulation (LES) to a large extent. Many SGS models are based on an isotropic description of the SGS motions. However, SGS turbulence is not always isotropic. Near-wall SGS motions in wall-bounded turbulent flows is an example of such. In that case, the quality of LES largely depend on the grid resolution and the SGS modeling used. On the other hand, one could speculate that dependence of LES results on the resolution would be less if the SGS model is able to properly take into account the anisotropy of SGS stresses. In this paper, the influence of resolution on LES is investigated. Three SGS models are used, namely: the standard dynamic Smagorinsky model (DS) based on (Germano et al., 1991) and modifications of (Lilly, 1992) which is an isotropic eddy viscosity model, the high-pass filtered dynamic Smagorinsky (HPF) model of (Stolz et al., 2005) which is based on the variational multiscale method and the recent explicit algebraic (EA) model of (Marstorp et al., 2009) which is capable of properly modeling the anisotropy of the SGS stresses. LES of channel flow is carried out using these SGS models at Re _τ =934, based on friction velocity and channel half width, and the results are compared to DNS data.