Exploring nonlinear subgrid-scale models and new characteristic length scales for large-eddy simulation

Abstract

We study subgrid-scale modeling for large-eddy simulation (LES) of anisotropic turbulent flows on anisotropic grids. In particular, we show how the addition of a velocity-gradient-based nonlinear model term to an eddy viscosity model provides a better representation of energy transfer. This is shown to lead to improved predictions of rotating and nonrotating homogeneous isotropic turbulence. Our research further focuses on calculation of the subgrid characteristic length, a key element for any eddy viscosity model. In the current work, we propose a new formulation of this quantity based on a Taylor series expansion of the subgrid stress tensor in the computational space. Numerical tests of decaying homogeneous isotropic turbulence and a plane-channel flow illustrate the robustness of this flow-dependent characteristic length scale with respect to mesh anisotropy.