Time-Space Correlations of Isotropic Turbulence by Lattice-Boltzmann-Based Large Eddy Simulation

Using combined method of large-eddy simulations with lattice Boltzmann (LES-LBM), an eddy-viscosity sub-grid scale (SGS) model has been developed, which is suitable for the LES-LBM framework to study space-time correlation of homogeneous isotropic turbulence. The lattice Boltzmann algorithm of 19-velocity D3Q19 lattice mode was implemented to calculate time evolution of the kinetic energy, the decay exponents of the dissipation rate, the instantaneous energy spectra and the high-order statistical quantities. Comparing with the evaluations of the model coefficients as a function of sub-grid activity obtained from direct numerical simulation (DNS) and other experiments, the obtained results from LES-LBM based new SGS model exhibit more satisfactory behavior than that of the classical one. Further, the abilities of several SGS models to predict the frequency-wave number energy spectra in turbulent flows were examined. It is found that the temporal de-correlation of smaller scales is determined by random sweeping motion of larger scales, the normalized frequency energy spectra of different wave number exhibit a common similarity to a certain extent and the sweeping velocity dominates the frequency-wave number energy spectra.