Influence of subgrid scale models on the buffer sublayer in channel flow

TL;DR

This study compares various subgrid-scale models in large-eddy simulations of channel flow, revealing their differing impacts on buffer layer turbulence and flow statistics at Re_ au=395.

Contribution

It provides a comparative analysis of SGS models, highlighting the influence of the buffer sublayer and identifying models that better capture turbulence fluctuations.

Findings

WALE and Sigma models outperform others in turbulence fluctuations

Constrained model slightly improves mean velocity

SGS dissipation strongly affects velocity fluctuations

Abstract

Subgrid-scale (SGS) models are critical in large-eddy simulations (LES) of turbulent flows. In this paper we conduct a comparative study on different SGS models, including one-k-equation, wall-adapting local eddy-viscosity (WALE), Sigma and shear-constrained model. Wall-resolved LES simulations of channel flows are performed with a finite volume code at shear Reynolds number Re_\tau = 395. In the simulations, the buffer sublayer turns out to be the most sensitive to the SGS model. Through the analysis of the mean velocity, the second-order moments, the SGS viscosity and the fluctuating vorticities, it is shown that the WALE and Sigma model outperform others significantly in terms of fluctuations while the constrained model improves slightly the mean velocity. The results also indicate that the SGS dissipation influences strongly the velocity fluctuations but not the mean flow nor the log-layer mismatch.