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

Abstract

We study subgrid-scale modeling for large-eddy simulation 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. %We furthermore show that spanwise-rotating turbulent plane-channel flows form a challenging test case for large-eddy simulation. 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.