Subgrid-scale model for large eddy simulations of incompressible turbulent flows within the lattice Boltzmann framework.

Large eddy simulations are a popular method for turbulent simulations because of their accuracy and efficiency. In this paper, a coupling algorithm is proposed that combines nonequilibrium moments (NM) and the volumetric strain-stretching (VSS) model within the framework of the lattice Boltzmann method (LBM). This algorithm establishes a relation between the NM and the eddy viscosity by using a special calculation form of the VSS model and Chapman-Enskog analysis. The coupling algorithm is validated in three typical flow cases: freely decaying homogeneous isotropic turbulence, homogeneous isotropic turbulence with body forces, and incompressible turbulent channel flow at Re_{τ}=180. The results show that the coupling algorithm is accurate and efficient when compared with the results of direct numerical simulations. Using calculation format of the eddy viscosity, a uniform calculation format is used for each grid point of the flow field during the modeling process. The modeling process uses only the local distribution function to obtain the local eddy viscosity coefficients without any additional processing on the boundary, while optimizing the memory access process to fit the inherent parallelism of the LBM. The efficiency of the calculation is improved by about 20% compared to the central difference method within the lattice Boltzmann framework for calculating the eddy viscosity.